Contact Dermatitis

The Diagnosis: Poroma

Histopathology showed an endophytic expansion of the epidermis by bland, uniform, basaloid epithelial cells with focal ductal differentiation and an abrupt transition with surrounding epidermal keratinocytes (Figure), consistent with a diagnosis of poroma. The patient elected to monitor the lesion rather than to have it excised.

Eccrine poroma, used interchangeably with the term poroma, is a rare benign adnexal tumor of the eccrine sweat glands resulting from proliferation of the acrosyringium.^1,2 It often occurs on the palms or soles, though it also can arise anywhere sweat glands are present.¹ Eccrine poromas often appear in middle-aged individuals as singular, well-circumscribed, red-brown papules or nodules.³ A characteristic feature is a shallow, cup-shaped depression within the larger papule or nodule.¹

Because the condition is benign and often asymptomatic, it can be safely monitored for progression.¹ However, if the lesion is symptomatic or located in a sensitive area, complete excision is curative.⁴ Eccrine poromas can recur, making close monitoring following excision important.⁵ The development of bleeding, itching, or pain in a previously asymptomatic lesion may indicate possible malignant transformation, which occurs in only 18% of cases.⁶

The differential diagnosis includes basal cell carcinoma, circumscribed acral hypokeratosis, Kaposi sarcoma, and pyogenic granuloma. Basal cell carcinoma is the most common type of skin cancer.⁷ In rare cases it has been shown to present on the palms or soles as a slowgrowing, reddish-pink papule or plaque with central ulceration. It typically is asymptomatic. Histopathology shows dermal nests of basaloid cells with peripheral palisading, stromal mucin, and peritumoral clefts. Treatment is surgical excision.⁷

Circumscribed acral hypokeratosis presents on the palms or soles as a solitary, shallow, well-defined lesion with a flat base and raised border.⁸ It often is red-pink in color and most frequently occurs in middle-aged women. Although the cause of the condition is unknown, it is thought to be the result of trauma or human papillomavirus infection.8 Biopsy results characteristically show hypokeratosis demarcated by a sharp and frayed cutoff from uninvolved acral skin with discrete hypogranulosis, dilated blood vessels in the papillary dermis, and slightly thickened collagen fibers in the reticular dermis.⁹ Surgical excision is a potential treatment option, as topical corticosteroids, retinoids, and calcipotriene have not been shown to be effective; spontaneous resolution has been reported.⁸

Kaposi sarcoma is a vascular neoplasm that is associated with human herpesvirus 8 infection.¹⁰ It typically presents on mucocutaneous sites and the lower extremities. Palmar involvement has been reported in rare cases, occurring as a solitary, well-demarcated, violaceous macule or patch that may be painful.^10-12 Characteristic histopathologic features include a proliferation in the dermis of slitlike vascular spaces and spindle cell proliferation.¹³ Treatment options include cryosurgery; pulsed dye laser; and topical, intralesional, or systemic chemotherapy agents, depending on the stage of the patient’s disease. Antiretroviral therapy is indicated for patients with Kaposi sarcoma secondary to AIDS.¹⁴

Pyogenic granuloma presents as a solitary red-brown or bluish-black papule or nodule that bleeds easily when manipulated.¹⁵ It commonly occurs following trauma, typically on the fingers, feet, and lips.⁶ Although benign, potential complications include ulceration and blood loss. Pyogenic granulomas can be treated via curettage and cautery, excision, cryosurgery, or pulsed dye laser.¹⁵

The Diagnosis: Poroma

Histopathology showed an endophytic expansion of the epidermis by bland, uniform, basaloid epithelial cells with focal ductal differentiation and an abrupt transition with surrounding epidermal keratinocytes (Figure), consistent with a diagnosis of poroma. The patient elected to monitor the lesion rather than to have it excised.

Eccrine poroma, used interchangeably with the term poroma, is a rare benign adnexal tumor of the eccrine sweat glands resulting from proliferation of the acrosyringium.^1,2 It often occurs on the palms or soles, though it also can arise anywhere sweat glands are present.¹ Eccrine poromas often appear in middle-aged individuals as singular, well-circumscribed, red-brown papules or nodules.³ A characteristic feature is a shallow, cup-shaped depression within the larger papule or nodule.¹

Because the condition is benign and often asymptomatic, it can be safely monitored for progression.¹ However, if the lesion is symptomatic or located in a sensitive area, complete excision is curative.⁴ Eccrine poromas can recur, making close monitoring following excision important.⁵ The development of bleeding, itching, or pain in a previously asymptomatic lesion may indicate possible malignant transformation, which occurs in only 18% of cases.⁶

The differential diagnosis includes basal cell carcinoma, circumscribed acral hypokeratosis, Kaposi sarcoma, and pyogenic granuloma. Basal cell carcinoma is the most common type of skin cancer.⁷ In rare cases it has been shown to present on the palms or soles as a slowgrowing, reddish-pink papule or plaque with central ulceration. It typically is asymptomatic. Histopathology shows dermal nests of basaloid cells with peripheral palisading, stromal mucin, and peritumoral clefts. Treatment is surgical excision.⁷

Circumscribed acral hypokeratosis presents on the palms or soles as a solitary, shallow, well-defined lesion with a flat base and raised border.⁸ It often is red-pink in color and most frequently occurs in middle-aged women. Although the cause of the condition is unknown, it is thought to be the result of trauma or human papillomavirus infection.8 Biopsy results characteristically show hypokeratosis demarcated by a sharp and frayed cutoff from uninvolved acral skin with discrete hypogranulosis, dilated blood vessels in the papillary dermis, and slightly thickened collagen fibers in the reticular dermis.⁹ Surgical excision is a potential treatment option, as topical corticosteroids, retinoids, and calcipotriene have not been shown to be effective; spontaneous resolution has been reported.⁸

Kaposi sarcoma is a vascular neoplasm that is associated with human herpesvirus 8 infection.¹⁰ It typically presents on mucocutaneous sites and the lower extremities. Palmar involvement has been reported in rare cases, occurring as a solitary, well-demarcated, violaceous macule or patch that may be painful.^10-12 Characteristic histopathologic features include a proliferation in the dermis of slitlike vascular spaces and spindle cell proliferation.¹³ Treatment options include cryosurgery; pulsed dye laser; and topical, intralesional, or systemic chemotherapy agents, depending on the stage of the patient’s disease. Antiretroviral therapy is indicated for patients with Kaposi sarcoma secondary to AIDS.¹⁴

Pyogenic granuloma presents as a solitary red-brown or bluish-black papule or nodule that bleeds easily when manipulated.¹⁵ It commonly occurs following trauma, typically on the fingers, feet, and lips.⁶ Although benign, potential complications include ulceration and blood loss. Pyogenic granulomas can be treated via curettage and cautery, excision, cryosurgery, or pulsed dye laser.¹⁵

The Diagnosis: Poroma

Histopathology showed an endophytic expansion of the epidermis by bland, uniform, basaloid epithelial cells with focal ductal differentiation and an abrupt transition with surrounding epidermal keratinocytes (Figure), consistent with a diagnosis of poroma. The patient elected to monitor the lesion rather than to have it excised.

Eccrine poroma, used interchangeably with the term poroma, is a rare benign adnexal tumor of the eccrine sweat glands resulting from proliferation of the acrosyringium.^1,2 It often occurs on the palms or soles, though it also can arise anywhere sweat glands are present.¹ Eccrine poromas often appear in middle-aged individuals as singular, well-circumscribed, red-brown papules or nodules.³ A characteristic feature is a shallow, cup-shaped depression within the larger papule or nodule.¹

Because the condition is benign and often asymptomatic, it can be safely monitored for progression.¹ However, if the lesion is symptomatic or located in a sensitive area, complete excision is curative.⁴ Eccrine poromas can recur, making close monitoring following excision important.⁵ The development of bleeding, itching, or pain in a previously asymptomatic lesion may indicate possible malignant transformation, which occurs in only 18% of cases.⁶

The differential diagnosis includes basal cell carcinoma, circumscribed acral hypokeratosis, Kaposi sarcoma, and pyogenic granuloma. Basal cell carcinoma is the most common type of skin cancer.⁷ In rare cases it has been shown to present on the palms or soles as a slowgrowing, reddish-pink papule or plaque with central ulceration. It typically is asymptomatic. Histopathology shows dermal nests of basaloid cells with peripheral palisading, stromal mucin, and peritumoral clefts. Treatment is surgical excision.⁷

Circumscribed acral hypokeratosis presents on the palms or soles as a solitary, shallow, well-defined lesion with a flat base and raised border.⁸ It often is red-pink in color and most frequently occurs in middle-aged women. Although the cause of the condition is unknown, it is thought to be the result of trauma or human papillomavirus infection.8 Biopsy results characteristically show hypokeratosis demarcated by a sharp and frayed cutoff from uninvolved acral skin with discrete hypogranulosis, dilated blood vessels in the papillary dermis, and slightly thickened collagen fibers in the reticular dermis.⁹ Surgical excision is a potential treatment option, as topical corticosteroids, retinoids, and calcipotriene have not been shown to be effective; spontaneous resolution has been reported.⁸

Kaposi sarcoma is a vascular neoplasm that is associated with human herpesvirus 8 infection.¹⁰ It typically presents on mucocutaneous sites and the lower extremities. Palmar involvement has been reported in rare cases, occurring as a solitary, well-demarcated, violaceous macule or patch that may be painful.^10-12 Characteristic histopathologic features include a proliferation in the dermis of slitlike vascular spaces and spindle cell proliferation.¹³ Treatment options include cryosurgery; pulsed dye laser; and topical, intralesional, or systemic chemotherapy agents, depending on the stage of the patient’s disease. Antiretroviral therapy is indicated for patients with Kaposi sarcoma secondary to AIDS.¹⁴

Pyogenic granuloma presents as a solitary red-brown or bluish-black papule or nodule that bleeds easily when manipulated.¹⁵ It commonly occurs following trauma, typically on the fingers, feet, and lips.⁶ Although benign, potential complications include ulceration and blood loss. Pyogenic granulomas can be treated via curettage and cautery, excision, cryosurgery, or pulsed dye laser.¹⁵

Around 5% of patients treated with dupilumab (Dupixent) for moderate-to-severe atopic dermatitis experience musculoskeletal (MSK) symptoms, according to the results of a descriptive study.

The main MSK symptom seen in the observational cohort was enthesitis, but some patients also experienced arthritis and tenosynovitis a median of 17 weeks after starting dupilumab treatment. Together these symptoms represent a new MSK syndrome, say researchers from the United Kingdom.

“The pattern of MSK symptoms and signs is characteristic of psoriatic arthritis/peripheral spondyloarthritis,” Bruce Kirkham, MD, and collaborators report in Arthritis & Rheumatology.

“We started a few years ago and have been following the patients for quite a long time,” Dr. Kirkham, a consultant rheumatologist at Guy’s and St. Thomas’ NHS Foundation Trust, London, told this news organization.

Characterizing the MSK symptoms

Of 470 patients with atopic dermatitis who started treatment with dupilumab at Guy’s and St. Thomas’ NHS Foundation Trust between October 2018 and February 2021, 36 (7.65%) developed rheumatic symptoms and were referred to the rheumatology department. These individuals had their family history assessed and thorough MSK evaluations, which included antibody and inflammatory markers, ultrasound of the peripheral small joints, and MRI of the large joints and spine.

A total of 26 (5.5%) patients – 14 of whom were male – had inflammatory enthesitis, arthritis, and/or tenosynovitis. Of the others, seven had osteoarthritis and three had degenerative spine disease.

Enthesitis was the most common finding in those with rheumatic symptoms, occurring on its own in 11 patients, with arthritis in three patients, and tenosynovitis in two patients.  

These symptoms appeared 2-48 weeks after starting dupilumab treatment and were categorized as mild in 16 (61%) cases, moderate in six cases, and severe in four cases.

No specific predictors of the MSK symptoms seen were noted. Patient age, sex, duration of their atopic dermatitis, or how their skin condition had been previously treated did not help identify those who might develop rheumatic problems.
 

Conservative management approach

All patients had “outstanding” responses to treatment, Dr. Kirkham noted: The mean Eczema Area and Severity Index score before dupilumab treatment was 21, falling to 4.2 with treatment, indicating a mean 80% improvement.

Co-author Joseph Nathan, MBChB, of London North West Healthcare NHS Trust, who collaborated on the research while working within Dr. Kirkham’s group, said separately: “The concern that patients have is that when they start a medication and develop a side effect is that the medication is going to be stopped.”

Clinicians treating the patients took a conservative approach, prescribing NSAIDs such as cyclooxygenase-2 inhibitors or altering the frequency with which dupilumab was given.

With this approach, MSK symptoms resolved in 15 patients who remained on treatment and in seven who had to stop dupilumab. There were four patients, however, who had unresolved symptoms even once dupilumab treatment had been stopped.
 

Altering the local cytokine balance

Dupilumab is a monoclonal antibody that binds to the alpha subunit of the interleukin-4 receptor. This results in blocking the function of not only IL-4 but also IL-13.

Dr. Kirkham and colleagues think this might not only alter the balance of cytokines in the skin but also in the joints and entheses with IL-17, IL-23, or even tumor necrosis factor playing a possible role. Another thought is that many circulating T-cells in the skin move to the joints and entheses to trigger symptoms.

IL-13 inhibition does seem to be important, as another British research team, from the Centre for Epidemiology Versus Arthritis at the University of Manchester (England), has found.

At the recent annual meeting of the British Society for Rheumatology, Sizheng Steven Zhao, MBChB, PhD, and colleagues reported that among people who carried a genetic variant predisposing them to having low IL-13 function, there was a higher risk for inflammatory diseases such as psoriatic arthritis and other spondyloarthropathy-related diseases.

Sara Freeman/Frontline Medical News

Dermatology perspective

Approved by the U.S. Food and Drug Administration in 2017, dupilumab has since been hailed as a “breakthrough” in atopic dermatitis treatment. Given as a subcutaneous injection every 2 weeks, it provides a much-needed option for people who have moderate-to-severe disease and have tried other available treatments, including corticosteroids.

Dupilumab has since also been approved for asthma, chronic sinusitis with nasal polyposis, eosinophilic esophagitis, and prurigo nodularis and is used off-label for other skin conditions such as contact dermatitis, chronic spontaneous urticaria, and alopecia areata.

“Dupilumab, like a lot of medications for atopic dermatitis, is a relatively new drug, and we are still learning about its safety,” Joel M. Gelfand, MD, MSCE, of the University of Pennsylvania Perelman School of Medicine, Philadelphia, told this news organization.

“Inflammatory arthritis has been reported in patients treated with dupilumab, and this new study provides some useful estimates,” added Dr. Gelfand, who is a professor of dermatology and epidemiology and directs the Psoriasis and Phototherapy Treatment Center, Philadelphia.

“There was no control group,” Dr. Gelfand said, so “a causal relationship cannot be well established based on these data alone. The mechanism is not known but may result from a shifting of the immune system.”

Dr. Zhao observed: “We don’t know what the natural history of these adverse events is. We don’t know if stopping the drug early will prevent long-term adverse events. So, we don’t know if people will ultimately develop permanent psoriatic arthritis if we don’t intervene quick enough when we observe an adverse event.”

Being aware of the possibility of rheumatic side effects occurring with dupilumab and similar agents is key, Dr. Gelfand and Dr. Kirkham both said independently.

“I have personally seen this entity in my practice,” Dr. Gelfand said. “It is important to clinicians prescribing dupilumab to alert patients about this potential side effect and ask about joint symptoms in follow-up.”

Dr. Kirkham said: “Prescribers need to be aware of it, because up until now it’s been just very vaguely discussed as sort of aches and pains, arthralgias, and it’s a much more specific of a kind of syndrome of enthesitis, arthritis, tenosynovitis – a little like psoriatic arthritis.”

Not everyone has come across these side effects, however, as Steven Daveluy, MD, associate professor and dermatology program director at Wayne State University, Detroit, said in an interview.

“This article and the other case series both noted the musculoskeletal symptoms occurred in about 5% of patients, which surprised me since I haven’t seen it in my practice and have enough patients being treated with dupilumab that I would expect to see a case at that rate,” Dr. Daveluy said.

“The majority of cases are mild and respond to treatment with anti-inflammatories like naproxen, which is available over the counter. It’s likely that patients with a mild case could simply treat their pain with naproxen that’s already in their medicine cabinet until it resolves, never bringing it to the doctor’s attention,” he suggested.

“Dupilumab is still a safe and effective medication that can change the lives of patients suffering from atopic dermatitis,” he said.

“Awareness of this potential side effect can help dermatologists recognize it early and work together with patients to determine the best course of action.”

All research mentioned in this article was independently supported. Dr. Kirkham, Mr. Nathan, Dr. Zhao, and Dr. Daveluy report no relevant financial relationships. Dr. Gelfand has served as a consultant for numerous pharmaceutical companies and receives research grants from Amgen, Boehringer Ingelheim, and Pfizer. He is a co-patent holder of resiquimod for treatment of cutaneous T-cell lymphoma.

A version of this article first appeared on Medscape.com.

Around 5% of patients treated with dupilumab (Dupixent) for moderate-to-severe atopic dermatitis experience musculoskeletal (MSK) symptoms, according to the results of a descriptive study.

The main MSK symptom seen in the observational cohort was enthesitis, but some patients also experienced arthritis and tenosynovitis a median of 17 weeks after starting dupilumab treatment. Together these symptoms represent a new MSK syndrome, say researchers from the United Kingdom.

“The pattern of MSK symptoms and signs is characteristic of psoriatic arthritis/peripheral spondyloarthritis,” Bruce Kirkham, MD, and collaborators report in Arthritis & Rheumatology.

“We started a few years ago and have been following the patients for quite a long time,” Dr. Kirkham, a consultant rheumatologist at Guy’s and St. Thomas’ NHS Foundation Trust, London, told this news organization.

Characterizing the MSK symptoms

Of 470 patients with atopic dermatitis who started treatment with dupilumab at Guy’s and St. Thomas’ NHS Foundation Trust between October 2018 and February 2021, 36 (7.65%) developed rheumatic symptoms and were referred to the rheumatology department. These individuals had their family history assessed and thorough MSK evaluations, which included antibody and inflammatory markers, ultrasound of the peripheral small joints, and MRI of the large joints and spine.

A total of 26 (5.5%) patients – 14 of whom were male – had inflammatory enthesitis, arthritis, and/or tenosynovitis. Of the others, seven had osteoarthritis and three had degenerative spine disease.

Enthesitis was the most common finding in those with rheumatic symptoms, occurring on its own in 11 patients, with arthritis in three patients, and tenosynovitis in two patients.  

These symptoms appeared 2-48 weeks after starting dupilumab treatment and were categorized as mild in 16 (61%) cases, moderate in six cases, and severe in four cases.

No specific predictors of the MSK symptoms seen were noted. Patient age, sex, duration of their atopic dermatitis, or how their skin condition had been previously treated did not help identify those who might develop rheumatic problems.
 

Conservative management approach

All patients had “outstanding” responses to treatment, Dr. Kirkham noted: The mean Eczema Area and Severity Index score before dupilumab treatment was 21, falling to 4.2 with treatment, indicating a mean 80% improvement.

Co-author Joseph Nathan, MBChB, of London North West Healthcare NHS Trust, who collaborated on the research while working within Dr. Kirkham’s group, said separately: “The concern that patients have is that when they start a medication and develop a side effect is that the medication is going to be stopped.”

Clinicians treating the patients took a conservative approach, prescribing NSAIDs such as cyclooxygenase-2 inhibitors or altering the frequency with which dupilumab was given.

With this approach, MSK symptoms resolved in 15 patients who remained on treatment and in seven who had to stop dupilumab. There were four patients, however, who had unresolved symptoms even once dupilumab treatment had been stopped.
 

Altering the local cytokine balance

Dupilumab is a monoclonal antibody that binds to the alpha subunit of the interleukin-4 receptor. This results in blocking the function of not only IL-4 but also IL-13.

Dr. Kirkham and colleagues think this might not only alter the balance of cytokines in the skin but also in the joints and entheses with IL-17, IL-23, or even tumor necrosis factor playing a possible role. Another thought is that many circulating T-cells in the skin move to the joints and entheses to trigger symptoms.

IL-13 inhibition does seem to be important, as another British research team, from the Centre for Epidemiology Versus Arthritis at the University of Manchester (England), has found.

At the recent annual meeting of the British Society for Rheumatology, Sizheng Steven Zhao, MBChB, PhD, and colleagues reported that among people who carried a genetic variant predisposing them to having low IL-13 function, there was a higher risk for inflammatory diseases such as psoriatic arthritis and other spondyloarthropathy-related diseases.

Sara Freeman/Frontline Medical News

Dermatology perspective

Approved by the U.S. Food and Drug Administration in 2017, dupilumab has since been hailed as a “breakthrough” in atopic dermatitis treatment. Given as a subcutaneous injection every 2 weeks, it provides a much-needed option for people who have moderate-to-severe disease and have tried other available treatments, including corticosteroids.

Dupilumab has since also been approved for asthma, chronic sinusitis with nasal polyposis, eosinophilic esophagitis, and prurigo nodularis and is used off-label for other skin conditions such as contact dermatitis, chronic spontaneous urticaria, and alopecia areata.

“Dupilumab, like a lot of medications for atopic dermatitis, is a relatively new drug, and we are still learning about its safety,” Joel M. Gelfand, MD, MSCE, of the University of Pennsylvania Perelman School of Medicine, Philadelphia, told this news organization.

“Inflammatory arthritis has been reported in patients treated with dupilumab, and this new study provides some useful estimates,” added Dr. Gelfand, who is a professor of dermatology and epidemiology and directs the Psoriasis and Phototherapy Treatment Center, Philadelphia.

“There was no control group,” Dr. Gelfand said, so “a causal relationship cannot be well established based on these data alone. The mechanism is not known but may result from a shifting of the immune system.”

Dr. Zhao observed: “We don’t know what the natural history of these adverse events is. We don’t know if stopping the drug early will prevent long-term adverse events. So, we don’t know if people will ultimately develop permanent psoriatic arthritis if we don’t intervene quick enough when we observe an adverse event.”

Being aware of the possibility of rheumatic side effects occurring with dupilumab and similar agents is key, Dr. Gelfand and Dr. Kirkham both said independently.

“I have personally seen this entity in my practice,” Dr. Gelfand said. “It is important to clinicians prescribing dupilumab to alert patients about this potential side effect and ask about joint symptoms in follow-up.”

Dr. Kirkham said: “Prescribers need to be aware of it, because up until now it’s been just very vaguely discussed as sort of aches and pains, arthralgias, and it’s a much more specific of a kind of syndrome of enthesitis, arthritis, tenosynovitis – a little like psoriatic arthritis.”

Not everyone has come across these side effects, however, as Steven Daveluy, MD, associate professor and dermatology program director at Wayne State University, Detroit, said in an interview.

“This article and the other case series both noted the musculoskeletal symptoms occurred in about 5% of patients, which surprised me since I haven’t seen it in my practice and have enough patients being treated with dupilumab that I would expect to see a case at that rate,” Dr. Daveluy said.

“The majority of cases are mild and respond to treatment with anti-inflammatories like naproxen, which is available over the counter. It’s likely that patients with a mild case could simply treat their pain with naproxen that’s already in their medicine cabinet until it resolves, never bringing it to the doctor’s attention,” he suggested.

“Dupilumab is still a safe and effective medication that can change the lives of patients suffering from atopic dermatitis,” he said.

“Awareness of this potential side effect can help dermatologists recognize it early and work together with patients to determine the best course of action.”

All research mentioned in this article was independently supported. Dr. Kirkham, Mr. Nathan, Dr. Zhao, and Dr. Daveluy report no relevant financial relationships. Dr. Gelfand has served as a consultant for numerous pharmaceutical companies and receives research grants from Amgen, Boehringer Ingelheim, and Pfizer. He is a co-patent holder of resiquimod for treatment of cutaneous T-cell lymphoma.

A version of this article first appeared on Medscape.com.

Around 5% of patients treated with dupilumab (Dupixent) for moderate-to-severe atopic dermatitis experience musculoskeletal (MSK) symptoms, according to the results of a descriptive study.

The main MSK symptom seen in the observational cohort was enthesitis, but some patients also experienced arthritis and tenosynovitis a median of 17 weeks after starting dupilumab treatment. Together these symptoms represent a new MSK syndrome, say researchers from the United Kingdom.

“The pattern of MSK symptoms and signs is characteristic of psoriatic arthritis/peripheral spondyloarthritis,” Bruce Kirkham, MD, and collaborators report in Arthritis & Rheumatology.

“We started a few years ago and have been following the patients for quite a long time,” Dr. Kirkham, a consultant rheumatologist at Guy’s and St. Thomas’ NHS Foundation Trust, London, told this news organization.

Characterizing the MSK symptoms

Of 470 patients with atopic dermatitis who started treatment with dupilumab at Guy’s and St. Thomas’ NHS Foundation Trust between October 2018 and February 2021, 36 (7.65%) developed rheumatic symptoms and were referred to the rheumatology department. These individuals had their family history assessed and thorough MSK evaluations, which included antibody and inflammatory markers, ultrasound of the peripheral small joints, and MRI of the large joints and spine.

A total of 26 (5.5%) patients – 14 of whom were male – had inflammatory enthesitis, arthritis, and/or tenosynovitis. Of the others, seven had osteoarthritis and three had degenerative spine disease.

Enthesitis was the most common finding in those with rheumatic symptoms, occurring on its own in 11 patients, with arthritis in three patients, and tenosynovitis in two patients.  

These symptoms appeared 2-48 weeks after starting dupilumab treatment and were categorized as mild in 16 (61%) cases, moderate in six cases, and severe in four cases.

No specific predictors of the MSK symptoms seen were noted. Patient age, sex, duration of their atopic dermatitis, or how their skin condition had been previously treated did not help identify those who might develop rheumatic problems.
 

Conservative management approach

All patients had “outstanding” responses to treatment, Dr. Kirkham noted: The mean Eczema Area and Severity Index score before dupilumab treatment was 21, falling to 4.2 with treatment, indicating a mean 80% improvement.

Co-author Joseph Nathan, MBChB, of London North West Healthcare NHS Trust, who collaborated on the research while working within Dr. Kirkham’s group, said separately: “The concern that patients have is that when they start a medication and develop a side effect is that the medication is going to be stopped.”

Clinicians treating the patients took a conservative approach, prescribing NSAIDs such as cyclooxygenase-2 inhibitors or altering the frequency with which dupilumab was given.

With this approach, MSK symptoms resolved in 15 patients who remained on treatment and in seven who had to stop dupilumab. There were four patients, however, who had unresolved symptoms even once dupilumab treatment had been stopped.
 

Altering the local cytokine balance

Dupilumab is a monoclonal antibody that binds to the alpha subunit of the interleukin-4 receptor. This results in blocking the function of not only IL-4 but also IL-13.

Dr. Kirkham and colleagues think this might not only alter the balance of cytokines in the skin but also in the joints and entheses with IL-17, IL-23, or even tumor necrosis factor playing a possible role. Another thought is that many circulating T-cells in the skin move to the joints and entheses to trigger symptoms.

IL-13 inhibition does seem to be important, as another British research team, from the Centre for Epidemiology Versus Arthritis at the University of Manchester (England), has found.

At the recent annual meeting of the British Society for Rheumatology, Sizheng Steven Zhao, MBChB, PhD, and colleagues reported that among people who carried a genetic variant predisposing them to having low IL-13 function, there was a higher risk for inflammatory diseases such as psoriatic arthritis and other spondyloarthropathy-related diseases.

Sara Freeman/Frontline Medical News

Dermatology perspective

Approved by the U.S. Food and Drug Administration in 2017, dupilumab has since been hailed as a “breakthrough” in atopic dermatitis treatment. Given as a subcutaneous injection every 2 weeks, it provides a much-needed option for people who have moderate-to-severe disease and have tried other available treatments, including corticosteroids.

Dupilumab has since also been approved for asthma, chronic sinusitis with nasal polyposis, eosinophilic esophagitis, and prurigo nodularis and is used off-label for other skin conditions such as contact dermatitis, chronic spontaneous urticaria, and alopecia areata.

“Dupilumab, like a lot of medications for atopic dermatitis, is a relatively new drug, and we are still learning about its safety,” Joel M. Gelfand, MD, MSCE, of the University of Pennsylvania Perelman School of Medicine, Philadelphia, told this news organization.

“Inflammatory arthritis has been reported in patients treated with dupilumab, and this new study provides some useful estimates,” added Dr. Gelfand, who is a professor of dermatology and epidemiology and directs the Psoriasis and Phototherapy Treatment Center, Philadelphia.

“There was no control group,” Dr. Gelfand said, so “a causal relationship cannot be well established based on these data alone. The mechanism is not known but may result from a shifting of the immune system.”

Dr. Zhao observed: “We don’t know what the natural history of these adverse events is. We don’t know if stopping the drug early will prevent long-term adverse events. So, we don’t know if people will ultimately develop permanent psoriatic arthritis if we don’t intervene quick enough when we observe an adverse event.”

Being aware of the possibility of rheumatic side effects occurring with dupilumab and similar agents is key, Dr. Gelfand and Dr. Kirkham both said independently.

“I have personally seen this entity in my practice,” Dr. Gelfand said. “It is important to clinicians prescribing dupilumab to alert patients about this potential side effect and ask about joint symptoms in follow-up.”

Dr. Kirkham said: “Prescribers need to be aware of it, because up until now it’s been just very vaguely discussed as sort of aches and pains, arthralgias, and it’s a much more specific of a kind of syndrome of enthesitis, arthritis, tenosynovitis – a little like psoriatic arthritis.”

Not everyone has come across these side effects, however, as Steven Daveluy, MD, associate professor and dermatology program director at Wayne State University, Detroit, said in an interview.

“This article and the other case series both noted the musculoskeletal symptoms occurred in about 5% of patients, which surprised me since I haven’t seen it in my practice and have enough patients being treated with dupilumab that I would expect to see a case at that rate,” Dr. Daveluy said.

“The majority of cases are mild and respond to treatment with anti-inflammatories like naproxen, which is available over the counter. It’s likely that patients with a mild case could simply treat their pain with naproxen that’s already in their medicine cabinet until it resolves, never bringing it to the doctor’s attention,” he suggested.

“Dupilumab is still a safe and effective medication that can change the lives of patients suffering from atopic dermatitis,” he said.

“Awareness of this potential side effect can help dermatologists recognize it early and work together with patients to determine the best course of action.”

All research mentioned in this article was independently supported. Dr. Kirkham, Mr. Nathan, Dr. Zhao, and Dr. Daveluy report no relevant financial relationships. Dr. Gelfand has served as a consultant for numerous pharmaceutical companies and receives research grants from Amgen, Boehringer Ingelheim, and Pfizer. He is a co-patent holder of resiquimod for treatment of cutaneous T-cell lymphoma.

A version of this article first appeared on Medscape.com.

Diabetes devices represent a major advancement in the management of diabetes, but they can cause skin reactions that affect patient adherence and quality of life, Jennifer K. Chen, MD, said in a presentation at the annual meeting of the American Contact Dermatitis Society.

Advanced technologies used for the management of diabetes fall into three main categories, said Dr. Chen, of the department of dermatology, Stanford University, Redwood City, Calif. Continuous glucose monitoring (CGM) devices, which are worn on the body, collect glucose measurements. Continuous subcutaneous insulin infusion (CSII) devices are attached to the body via an infusion set and are now available as tubing-free patch pumps that are attached directly to the skin via a catheter. Glucose-responsive insulin delivery systems combine the sensing and delivery features of the other two types of devices.

Dr. Chen

Once thought to be rare, reports of skin complications related to diabetes devices have been increasing in recent years, she said. Some reports suggest that at any given time, skin complications may affect as many as one quarter to one half of patients who use these devices, “so this is an important issue,” she emphasized. “Skin reactions are a major factor in device discontinuation, so we as clinicians need to be really proactive about treating these reactions.”

Risk factors for skin complications related to diabetes devices include sensitization to the adhesive used with the devices, as well as prolonged exposure to the device, Dr. Chen said. Younger age also appears to be a risk factor, as is a compromised skin barrier in the area where the device is used.

Unfortunately, obtaining details on the specific adhesives and the raw materials used in these devices, so as to customize patch testing, remains a challenge, she said. “Patch testing initially was often negative to commercially available allergens, even while patients were testing positive to pieces of device adhesive,” she noted.
 

Consider isobornyl acrylate

An article published in 2017 in Contact Dermatitis was “a major breakthrough” in that it identified isobornyl acrylate (IBOA) as an allergen in connection with the Freestyle Libre, a CGM device that was relatively new at the time. The finding was serendipitous, Dr. Chen said. A patient being treated for suspected allergic contact dermatitis in connection with use of a Freestyle Libre device was tested for IBOA accidentally, after the nurse administering the patch test thought that this was part of the standard acrylate series, she explained.

Subsequently, researchers identified 15 patients who had experienced reactions to the Freestyle Libre; 12 of 13 patients who were patch tested for IBOA tested positive. IBOA was found throughout the device, particularly where the top and bottom plastic components were connected, Dr. Chen said. This suggested that the IBOA was in the device housing and had diffused into the adhesive that attached the device to the skin.

An article published in 2018 in the Journal of Diabetes Science described three patients who developed severe allergic contact dermatitis from IBOA while using a CGM device, Dr. Chen said. The investigators confirmed that there were no reactions to the adhesive itself, again suggesting that IBOA had diffused into the adhesive from other parts of the device.

Although the authors were bound by a confidentiality agreement regarding the individual adhesive components, “the authors noted most of the acrylates in the adhesive were not present in commercially available acrylate series for patch testing,” she said.

IBOA, the ACDS’ Allergen of the Year in 2020, is common in sealants, glues, and adhesives, Dr. Chen said. Although IBOA had been reported infrequently as an allergen, it has now been identified as a “potential culprit” behind skin reactions in many diabetes devices, including CSII and CGM devices, she added.

In addition, N,N-dimethylacrylamide (DMAA) is an allergen that has been identified in several diabetes devices and often occurs with IBOA in medical-grade UV-cured adhesives, Dr. Chen noted. Other allergens identified in diabetes devices include colophony, which is present in many adhesives, as well as other acrylates and epoxy resin.

Diabetes devices are constantly evolving. IBOA is no longer found in Freestyle Libre devices. It is important that clinicians stay up to date with the medical literature and advocate for partnership with device manufacturers, she emphasized.
 

Patch testing

When diabetes devices are suspected as the source of allergic contact dermatitis, a minimum of a baseline series that contains colophony at a concentration of 20% in petrolatum should be carried out, Dr. Chen said. Commercialized patch test trays, which include plastics, glues, acrylates, epoxy resins/isocyanates, and colophony derivatives, should be ideal. “Personal-care products should be included if they are potentially relevant,” she added.

Dr. Chen shared tables published in Contact Dermatitis in 2021 with examples of screening test series. She said to consider including screening for other allergens more recently discovered in diabetes devices, including 2,2’-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate (MBPA) 1.5% pet; dipropylene glycol diacrylate (DPGDA) 0.1% pet; and butylated hydroxytoluene (BHT) 2% pet.

Testing for monomethyl ether of hydroquinone should also be considered; this may be included in the test preparations for IBOA and DMAA.
 

Management strategies

For patients who experience skin reactions to their diabetes devices, consideration may given to relocating the device to another area of skin or changing sensors more frequently, according to Dr. Chen.

For some patients, the reaction can be managed with corticosteroid cream, ointment, solution, or nasal spray. Topical antibiotics or topical antihistamines can be helpful, as can barrier dressings, solutions, or sprays, she said. The best solution is to change to a device that does not have the culprit allergen, “but that is difficult, since we don’t know what is in these devices,” she added. Good alternatives include the Eversense CGM device or devices that have been demonstrated not to contain IBOA, such as the Freestyle Libre 2 or the newer version of the Omnipod, an insulin delivery system

Looking ahead, Dr. Chen said that “mandatory labeling is needed, as devices with the same name may have different compositions, depending on the date of manufacture.” Allergens relevant to people with diabetes are constantly evolving, and many are still unidentified, so clinicians and manufacturers need to work together to identify the culprit allergens and their sources, she said.

Dr. Chen has served as principal investigator or subinvestigator for Amgen, AbbVie, and Sanofi Regeneron and as a consultant for Purity Brands.
 

A version of this article first appeared on Medscape.com.

Diabetes devices represent a major advancement in the management of diabetes, but they can cause skin reactions that affect patient adherence and quality of life, Jennifer K. Chen, MD, said in a presentation at the annual meeting of the American Contact Dermatitis Society.

Advanced technologies used for the management of diabetes fall into three main categories, said Dr. Chen, of the department of dermatology, Stanford University, Redwood City, Calif. Continuous glucose monitoring (CGM) devices, which are worn on the body, collect glucose measurements. Continuous subcutaneous insulin infusion (CSII) devices are attached to the body via an infusion set and are now available as tubing-free patch pumps that are attached directly to the skin via a catheter. Glucose-responsive insulin delivery systems combine the sensing and delivery features of the other two types of devices.

Dr. Chen

Once thought to be rare, reports of skin complications related to diabetes devices have been increasing in recent years, she said. Some reports suggest that at any given time, skin complications may affect as many as one quarter to one half of patients who use these devices, “so this is an important issue,” she emphasized. “Skin reactions are a major factor in device discontinuation, so we as clinicians need to be really proactive about treating these reactions.”

Risk factors for skin complications related to diabetes devices include sensitization to the adhesive used with the devices, as well as prolonged exposure to the device, Dr. Chen said. Younger age also appears to be a risk factor, as is a compromised skin barrier in the area where the device is used.

Unfortunately, obtaining details on the specific adhesives and the raw materials used in these devices, so as to customize patch testing, remains a challenge, she said. “Patch testing initially was often negative to commercially available allergens, even while patients were testing positive to pieces of device adhesive,” she noted.
 

Consider isobornyl acrylate

An article published in 2017 in Contact Dermatitis was “a major breakthrough” in that it identified isobornyl acrylate (IBOA) as an allergen in connection with the Freestyle Libre, a CGM device that was relatively new at the time. The finding was serendipitous, Dr. Chen said. A patient being treated for suspected allergic contact dermatitis in connection with use of a Freestyle Libre device was tested for IBOA accidentally, after the nurse administering the patch test thought that this was part of the standard acrylate series, she explained.

Subsequently, researchers identified 15 patients who had experienced reactions to the Freestyle Libre; 12 of 13 patients who were patch tested for IBOA tested positive. IBOA was found throughout the device, particularly where the top and bottom plastic components were connected, Dr. Chen said. This suggested that the IBOA was in the device housing and had diffused into the adhesive that attached the device to the skin.

An article published in 2018 in the Journal of Diabetes Science described three patients who developed severe allergic contact dermatitis from IBOA while using a CGM device, Dr. Chen said. The investigators confirmed that there were no reactions to the adhesive itself, again suggesting that IBOA had diffused into the adhesive from other parts of the device.

Although the authors were bound by a confidentiality agreement regarding the individual adhesive components, “the authors noted most of the acrylates in the adhesive were not present in commercially available acrylate series for patch testing,” she said.

IBOA, the ACDS’ Allergen of the Year in 2020, is common in sealants, glues, and adhesives, Dr. Chen said. Although IBOA had been reported infrequently as an allergen, it has now been identified as a “potential culprit” behind skin reactions in many diabetes devices, including CSII and CGM devices, she added.

In addition, N,N-dimethylacrylamide (DMAA) is an allergen that has been identified in several diabetes devices and often occurs with IBOA in medical-grade UV-cured adhesives, Dr. Chen noted. Other allergens identified in diabetes devices include colophony, which is present in many adhesives, as well as other acrylates and epoxy resin.

Diabetes devices are constantly evolving. IBOA is no longer found in Freestyle Libre devices. It is important that clinicians stay up to date with the medical literature and advocate for partnership with device manufacturers, she emphasized.
 

Patch testing

When diabetes devices are suspected as the source of allergic contact dermatitis, a minimum of a baseline series that contains colophony at a concentration of 20% in petrolatum should be carried out, Dr. Chen said. Commercialized patch test trays, which include plastics, glues, acrylates, epoxy resins/isocyanates, and colophony derivatives, should be ideal. “Personal-care products should be included if they are potentially relevant,” she added.

Dr. Chen shared tables published in Contact Dermatitis in 2021 with examples of screening test series. She said to consider including screening for other allergens more recently discovered in diabetes devices, including 2,2’-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate (MBPA) 1.5% pet; dipropylene glycol diacrylate (DPGDA) 0.1% pet; and butylated hydroxytoluene (BHT) 2% pet.

Testing for monomethyl ether of hydroquinone should also be considered; this may be included in the test preparations for IBOA and DMAA.
 

Management strategies

For patients who experience skin reactions to their diabetes devices, consideration may given to relocating the device to another area of skin or changing sensors more frequently, according to Dr. Chen.

For some patients, the reaction can be managed with corticosteroid cream, ointment, solution, or nasal spray. Topical antibiotics or topical antihistamines can be helpful, as can barrier dressings, solutions, or sprays, she said. The best solution is to change to a device that does not have the culprit allergen, “but that is difficult, since we don’t know what is in these devices,” she added. Good alternatives include the Eversense CGM device or devices that have been demonstrated not to contain IBOA, such as the Freestyle Libre 2 or the newer version of the Omnipod, an insulin delivery system

Looking ahead, Dr. Chen said that “mandatory labeling is needed, as devices with the same name may have different compositions, depending on the date of manufacture.” Allergens relevant to people with diabetes are constantly evolving, and many are still unidentified, so clinicians and manufacturers need to work together to identify the culprit allergens and their sources, she said.

Dr. Chen has served as principal investigator or subinvestigator for Amgen, AbbVie, and Sanofi Regeneron and as a consultant for Purity Brands.
 

A version of this article first appeared on Medscape.com.

Diabetes devices represent a major advancement in the management of diabetes, but they can cause skin reactions that affect patient adherence and quality of life, Jennifer K. Chen, MD, said in a presentation at the annual meeting of the American Contact Dermatitis Society.

Advanced technologies used for the management of diabetes fall into three main categories, said Dr. Chen, of the department of dermatology, Stanford University, Redwood City, Calif. Continuous glucose monitoring (CGM) devices, which are worn on the body, collect glucose measurements. Continuous subcutaneous insulin infusion (CSII) devices are attached to the body via an infusion set and are now available as tubing-free patch pumps that are attached directly to the skin via a catheter. Glucose-responsive insulin delivery systems combine the sensing and delivery features of the other two types of devices.

Dr. Chen

Once thought to be rare, reports of skin complications related to diabetes devices have been increasing in recent years, she said. Some reports suggest that at any given time, skin complications may affect as many as one quarter to one half of patients who use these devices, “so this is an important issue,” she emphasized. “Skin reactions are a major factor in device discontinuation, so we as clinicians need to be really proactive about treating these reactions.”

Risk factors for skin complications related to diabetes devices include sensitization to the adhesive used with the devices, as well as prolonged exposure to the device, Dr. Chen said. Younger age also appears to be a risk factor, as is a compromised skin barrier in the area where the device is used.

Unfortunately, obtaining details on the specific adhesives and the raw materials used in these devices, so as to customize patch testing, remains a challenge, she said. “Patch testing initially was often negative to commercially available allergens, even while patients were testing positive to pieces of device adhesive,” she noted.
 

Consider isobornyl acrylate

An article published in 2017 in Contact Dermatitis was “a major breakthrough” in that it identified isobornyl acrylate (IBOA) as an allergen in connection with the Freestyle Libre, a CGM device that was relatively new at the time. The finding was serendipitous, Dr. Chen said. A patient being treated for suspected allergic contact dermatitis in connection with use of a Freestyle Libre device was tested for IBOA accidentally, after the nurse administering the patch test thought that this was part of the standard acrylate series, she explained.

Subsequently, researchers identified 15 patients who had experienced reactions to the Freestyle Libre; 12 of 13 patients who were patch tested for IBOA tested positive. IBOA was found throughout the device, particularly where the top and bottom plastic components were connected, Dr. Chen said. This suggested that the IBOA was in the device housing and had diffused into the adhesive that attached the device to the skin.

An article published in 2018 in the Journal of Diabetes Science described three patients who developed severe allergic contact dermatitis from IBOA while using a CGM device, Dr. Chen said. The investigators confirmed that there were no reactions to the adhesive itself, again suggesting that IBOA had diffused into the adhesive from other parts of the device.

Although the authors were bound by a confidentiality agreement regarding the individual adhesive components, “the authors noted most of the acrylates in the adhesive were not present in commercially available acrylate series for patch testing,” she said.

IBOA, the ACDS’ Allergen of the Year in 2020, is common in sealants, glues, and adhesives, Dr. Chen said. Although IBOA had been reported infrequently as an allergen, it has now been identified as a “potential culprit” behind skin reactions in many diabetes devices, including CSII and CGM devices, she added.

In addition, N,N-dimethylacrylamide (DMAA) is an allergen that has been identified in several diabetes devices and often occurs with IBOA in medical-grade UV-cured adhesives, Dr. Chen noted. Other allergens identified in diabetes devices include colophony, which is present in many adhesives, as well as other acrylates and epoxy resin.

Diabetes devices are constantly evolving. IBOA is no longer found in Freestyle Libre devices. It is important that clinicians stay up to date with the medical literature and advocate for partnership with device manufacturers, she emphasized.
 

Patch testing

When diabetes devices are suspected as the source of allergic contact dermatitis, a minimum of a baseline series that contains colophony at a concentration of 20% in petrolatum should be carried out, Dr. Chen said. Commercialized patch test trays, which include plastics, glues, acrylates, epoxy resins/isocyanates, and colophony derivatives, should be ideal. “Personal-care products should be included if they are potentially relevant,” she added.

Dr. Chen shared tables published in Contact Dermatitis in 2021 with examples of screening test series. She said to consider including screening for other allergens more recently discovered in diabetes devices, including 2,2’-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate (MBPA) 1.5% pet; dipropylene glycol diacrylate (DPGDA) 0.1% pet; and butylated hydroxytoluene (BHT) 2% pet.

Testing for monomethyl ether of hydroquinone should also be considered; this may be included in the test preparations for IBOA and DMAA.
 

Management strategies

For patients who experience skin reactions to their diabetes devices, consideration may given to relocating the device to another area of skin or changing sensors more frequently, according to Dr. Chen.

For some patients, the reaction can be managed with corticosteroid cream, ointment, solution, or nasal spray. Topical antibiotics or topical antihistamines can be helpful, as can barrier dressings, solutions, or sprays, she said. The best solution is to change to a device that does not have the culprit allergen, “but that is difficult, since we don’t know what is in these devices,” she added. Good alternatives include the Eversense CGM device or devices that have been demonstrated not to contain IBOA, such as the Freestyle Libre 2 or the newer version of the Omnipod, an insulin delivery system

Looking ahead, Dr. Chen said that “mandatory labeling is needed, as devices with the same name may have different compositions, depending on the date of manufacture.” Allergens relevant to people with diabetes are constantly evolving, and many are still unidentified, so clinicians and manufacturers need to work together to identify the culprit allergens and their sources, she said.

Dr. Chen has served as principal investigator or subinvestigator for Amgen, AbbVie, and Sanofi Regeneron and as a consultant for Purity Brands.
 

A version of this article first appeared on Medscape.com.

Consider popular nutritional supplements as a potential source of allergic reactions if the cause of the reaction is otherwise unknown, Alison Ehrlich, MD, said at the annual meeting of the American Contact Dermatitis Society.

Sherri Holdridge

Allergens may be hidden in a range of supplement products, from colorings in vitamin C powders to some vitamins used in hair products and other products.

“In general, our patients do not tell us what supplements they are taking,” said Dr. Ehrlich, a dermatologist who practices in Washington, D.C. Antiaging, sleep, and weight loss/weight control supplements are among the most popular, she said.

Surveys have shown that many patients do not discuss supplement use with their health care providers, in part because they believe their providers would disapprove of supplement use, and patients are not educated about supplements, she said. “This is definitely an area that we should try to learn more about,” she added.

Current regulations regarding dietary supplements stem from the Dietary Supplement Health and Education Act of 1994, which defined dietary supplements as distinct from meals but regulated them as a category of food, not as medications. Dietary supplements can be vitamins, minerals, herbs, and extracts, Dr. Ehrlich said.

“There is not a lot of safety wrapped around how supplements come onto the market,” she explained. “It is not the manufacturer’s responsibility to test these products and make sure they are safe. When they get pulled off the market, it is because safety reports are getting back to the FDA.”

Consequently, a detailed history of supplement use is important, as it may reveal possible allergens as the cause of previously unidentified reactions, she said.

Dr. Ehrlich shared a case involving a patient who claimed to have had a reaction to a “Prevage-like” product that was labeled as a crepe repair cream. Listed among the product’s ingredients was idebenone, a synthetic version of the popular antioxidant known as Coenzyme Q.
 

Be wary of vitamins

Another potential source of allergy is vitamin C supplements, which became especially popular during the pandemic as people sought additional immune system support, Dr. Ehrlich noted. “What kind of vitamin C product our patients are taking is important,” she said. For example, some vitamin C powders contain coloring agents, such as carmine. Some also contain gelatin, which may cause an allergic reaction in individuals with alpha-gal syndrome, she added.

Sally Koch Kubetin/MDedge News

In general, water-soluble vitamins such as vitamins B1 to B9, B12, and C are more likely to cause an immediate reaction, Dr. Ehrlich said. Fat-soluble vitamins, such as vitamins A, D, E, and K, are more likely to cause a delayed reaction of allergic contact dermatitis.

Dr. Ehrlich described some unusual reactions to vitamins that have been reported, including a systemic allergy associated with vitamin B1 (thiamine), burning mouth syndrome associated with vitamin B3 (nicotinate), contact urticaria associated with vitamin B5 (panthenol), systemic allergy and generalized ACD associated with vitamin E (tocopherol), and erythema multiforme–like ACD associated with vitamin K1.

Notably, vitamin B5 has been associated with ACD as an ingredient in hair products, moisturizers, and wound care products, as well as B-complex vitamins and fortified foods, Dr. Ehrlich said.

Herbs and spices can act as allergens as well. Turmeric is a spice that has become a popular supplement ingredient, she said. Turmeric and curcumin (found in turmeric) can be used as a dye for its yellow color as well as a flavoring but has been associated with allergic reactions. Another popular herbal supplement, ginkgo biloba, has been marketed as a product that improves memory and cognition. It is available in pill form and in herbal teas.

“It’s really important to think about what herbal products our patients are taking, and not just in pill form,” Dr. Ehrlich said. “We need to expand our thoughts on what the herbs are in.”
 

Consider food additives as allergens

Food additives, in the form of colorants, preservatives, or flavoring agents, can cause allergic reactions, Dr. Ehrlich noted.

The question of whether food-additive contact sensitivity has a role in the occurrence of atopic dermatitis (AD) in children remains unclear, she said. However, a study published in 2020 found that 62% of children with AD had positive patch test reactions to at least one food-additive allergen, compared with 20% of children without AD. The additives responsible for the most reactions were azorubine (24.4%); formic acid (15.6%); and carmine, cochineal red, and amaranth (13.3% for each).

Common colorant culprits in allergic reactions include carmine, annatto, tartrazine, and spices (such as paprika and saffron), Dr. Ehrlich said. Carmine is used in meat to prevent photo-oxidation and to preserve a red color, and it has other uses as well, she said. Carmine has been associated with ACD, AD flares, and immediate hypersensitivity. Annatto is used in foods, including processed foods, butter, and cheese, to provide a yellow color. It is also found in some lipsticks and has been associated with urticaria and angioedema, she noted.

Food preservatives that have been associated with allergic reactions include butylated hydroxyanisole and sulfites, Dr. Ehrlich said. Sulfites are used to prevent food from turning brown, and it may be present in dried fruit, fruit juice, molasses, pickled foods, vinegar, and wine.

Reports of ACD in response to sodium metabisulfite have been increasing, she noted. Other sulfite reactions may occur with exposure to other products, such as cosmetics, body washes, and swimming pool water, she said.

Awareness of allergens in supplements is important “because the number of our patients taking supplements for different reasons is increasing” and allergens in supplements could account for flares, Dr. Ehrlich said. Clinicians should encourage patients to tell them what supplements they use. Clinicians should review the ingredients in these supplements with their patients to identify potential allergens that may be causing reactions, she advised.

Dr. Ehrlich has disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Consider popular nutritional supplements as a potential source of allergic reactions if the cause of the reaction is otherwise unknown, Alison Ehrlich, MD, said at the annual meeting of the American Contact Dermatitis Society.

Sherri Holdridge

Allergens may be hidden in a range of supplement products, from colorings in vitamin C powders to some vitamins used in hair products and other products.

“In general, our patients do not tell us what supplements they are taking,” said Dr. Ehrlich, a dermatologist who practices in Washington, D.C. Antiaging, sleep, and weight loss/weight control supplements are among the most popular, she said.

Surveys have shown that many patients do not discuss supplement use with their health care providers, in part because they believe their providers would disapprove of supplement use, and patients are not educated about supplements, she said. “This is definitely an area that we should try to learn more about,” she added.

Current regulations regarding dietary supplements stem from the Dietary Supplement Health and Education Act of 1994, which defined dietary supplements as distinct from meals but regulated them as a category of food, not as medications. Dietary supplements can be vitamins, minerals, herbs, and extracts, Dr. Ehrlich said.

“There is not a lot of safety wrapped around how supplements come onto the market,” she explained. “It is not the manufacturer’s responsibility to test these products and make sure they are safe. When they get pulled off the market, it is because safety reports are getting back to the FDA.”

Consequently, a detailed history of supplement use is important, as it may reveal possible allergens as the cause of previously unidentified reactions, she said.

Dr. Ehrlich shared a case involving a patient who claimed to have had a reaction to a “Prevage-like” product that was labeled as a crepe repair cream. Listed among the product’s ingredients was idebenone, a synthetic version of the popular antioxidant known as Coenzyme Q.
 

Be wary of vitamins

Another potential source of allergy is vitamin C supplements, which became especially popular during the pandemic as people sought additional immune system support, Dr. Ehrlich noted. “What kind of vitamin C product our patients are taking is important,” she said. For example, some vitamin C powders contain coloring agents, such as carmine. Some also contain gelatin, which may cause an allergic reaction in individuals with alpha-gal syndrome, she added.

Sally Koch Kubetin/MDedge News

In general, water-soluble vitamins such as vitamins B1 to B9, B12, and C are more likely to cause an immediate reaction, Dr. Ehrlich said. Fat-soluble vitamins, such as vitamins A, D, E, and K, are more likely to cause a delayed reaction of allergic contact dermatitis.

Dr. Ehrlich described some unusual reactions to vitamins that have been reported, including a systemic allergy associated with vitamin B1 (thiamine), burning mouth syndrome associated with vitamin B3 (nicotinate), contact urticaria associated with vitamin B5 (panthenol), systemic allergy and generalized ACD associated with vitamin E (tocopherol), and erythema multiforme–like ACD associated with vitamin K1.

Notably, vitamin B5 has been associated with ACD as an ingredient in hair products, moisturizers, and wound care products, as well as B-complex vitamins and fortified foods, Dr. Ehrlich said.

Herbs and spices can act as allergens as well. Turmeric is a spice that has become a popular supplement ingredient, she said. Turmeric and curcumin (found in turmeric) can be used as a dye for its yellow color as well as a flavoring but has been associated with allergic reactions. Another popular herbal supplement, ginkgo biloba, has been marketed as a product that improves memory and cognition. It is available in pill form and in herbal teas.

“It’s really important to think about what herbal products our patients are taking, and not just in pill form,” Dr. Ehrlich said. “We need to expand our thoughts on what the herbs are in.”
 

Consider food additives as allergens

Food additives, in the form of colorants, preservatives, or flavoring agents, can cause allergic reactions, Dr. Ehrlich noted.

The question of whether food-additive contact sensitivity has a role in the occurrence of atopic dermatitis (AD) in children remains unclear, she said. However, a study published in 2020 found that 62% of children with AD had positive patch test reactions to at least one food-additive allergen, compared with 20% of children without AD. The additives responsible for the most reactions were azorubine (24.4%); formic acid (15.6%); and carmine, cochineal red, and amaranth (13.3% for each).

Common colorant culprits in allergic reactions include carmine, annatto, tartrazine, and spices (such as paprika and saffron), Dr. Ehrlich said. Carmine is used in meat to prevent photo-oxidation and to preserve a red color, and it has other uses as well, she said. Carmine has been associated with ACD, AD flares, and immediate hypersensitivity. Annatto is used in foods, including processed foods, butter, and cheese, to provide a yellow color. It is also found in some lipsticks and has been associated with urticaria and angioedema, she noted.

Food preservatives that have been associated with allergic reactions include butylated hydroxyanisole and sulfites, Dr. Ehrlich said. Sulfites are used to prevent food from turning brown, and it may be present in dried fruit, fruit juice, molasses, pickled foods, vinegar, and wine.

Reports of ACD in response to sodium metabisulfite have been increasing, she noted. Other sulfite reactions may occur with exposure to other products, such as cosmetics, body washes, and swimming pool water, she said.

Awareness of allergens in supplements is important “because the number of our patients taking supplements for different reasons is increasing” and allergens in supplements could account for flares, Dr. Ehrlich said. Clinicians should encourage patients to tell them what supplements they use. Clinicians should review the ingredients in these supplements with their patients to identify potential allergens that may be causing reactions, she advised.

Dr. Ehrlich has disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Consider popular nutritional supplements as a potential source of allergic reactions if the cause of the reaction is otherwise unknown, Alison Ehrlich, MD, said at the annual meeting of the American Contact Dermatitis Society.

Sherri Holdridge

Allergens may be hidden in a range of supplement products, from colorings in vitamin C powders to some vitamins used in hair products and other products.

“In general, our patients do not tell us what supplements they are taking,” said Dr. Ehrlich, a dermatologist who practices in Washington, D.C. Antiaging, sleep, and weight loss/weight control supplements are among the most popular, she said.

Surveys have shown that many patients do not discuss supplement use with their health care providers, in part because they believe their providers would disapprove of supplement use, and patients are not educated about supplements, she said. “This is definitely an area that we should try to learn more about,” she added.

Current regulations regarding dietary supplements stem from the Dietary Supplement Health and Education Act of 1994, which defined dietary supplements as distinct from meals but regulated them as a category of food, not as medications. Dietary supplements can be vitamins, minerals, herbs, and extracts, Dr. Ehrlich said.

“There is not a lot of safety wrapped around how supplements come onto the market,” she explained. “It is not the manufacturer’s responsibility to test these products and make sure they are safe. When they get pulled off the market, it is because safety reports are getting back to the FDA.”

Consequently, a detailed history of supplement use is important, as it may reveal possible allergens as the cause of previously unidentified reactions, she said.

Dr. Ehrlich shared a case involving a patient who claimed to have had a reaction to a “Prevage-like” product that was labeled as a crepe repair cream. Listed among the product’s ingredients was idebenone, a synthetic version of the popular antioxidant known as Coenzyme Q.
 

Be wary of vitamins

Another potential source of allergy is vitamin C supplements, which became especially popular during the pandemic as people sought additional immune system support, Dr. Ehrlich noted. “What kind of vitamin C product our patients are taking is important,” she said. For example, some vitamin C powders contain coloring agents, such as carmine. Some also contain gelatin, which may cause an allergic reaction in individuals with alpha-gal syndrome, she added.

Sally Koch Kubetin/MDedge News

In general, water-soluble vitamins such as vitamins B1 to B9, B12, and C are more likely to cause an immediate reaction, Dr. Ehrlich said. Fat-soluble vitamins, such as vitamins A, D, E, and K, are more likely to cause a delayed reaction of allergic contact dermatitis.

Dr. Ehrlich described some unusual reactions to vitamins that have been reported, including a systemic allergy associated with vitamin B1 (thiamine), burning mouth syndrome associated with vitamin B3 (nicotinate), contact urticaria associated with vitamin B5 (panthenol), systemic allergy and generalized ACD associated with vitamin E (tocopherol), and erythema multiforme–like ACD associated with vitamin K1.

Notably, vitamin B5 has been associated with ACD as an ingredient in hair products, moisturizers, and wound care products, as well as B-complex vitamins and fortified foods, Dr. Ehrlich said.

Herbs and spices can act as allergens as well. Turmeric is a spice that has become a popular supplement ingredient, she said. Turmeric and curcumin (found in turmeric) can be used as a dye for its yellow color as well as a flavoring but has been associated with allergic reactions. Another popular herbal supplement, ginkgo biloba, has been marketed as a product that improves memory and cognition. It is available in pill form and in herbal teas.

“It’s really important to think about what herbal products our patients are taking, and not just in pill form,” Dr. Ehrlich said. “We need to expand our thoughts on what the herbs are in.”
 

Consider food additives as allergens

Food additives, in the form of colorants, preservatives, or flavoring agents, can cause allergic reactions, Dr. Ehrlich noted.

The question of whether food-additive contact sensitivity has a role in the occurrence of atopic dermatitis (AD) in children remains unclear, she said. However, a study published in 2020 found that 62% of children with AD had positive patch test reactions to at least one food-additive allergen, compared with 20% of children without AD. The additives responsible for the most reactions were azorubine (24.4%); formic acid (15.6%); and carmine, cochineal red, and amaranth (13.3% for each).

Common colorant culprits in allergic reactions include carmine, annatto, tartrazine, and spices (such as paprika and saffron), Dr. Ehrlich said. Carmine is used in meat to prevent photo-oxidation and to preserve a red color, and it has other uses as well, she said. Carmine has been associated with ACD, AD flares, and immediate hypersensitivity. Annatto is used in foods, including processed foods, butter, and cheese, to provide a yellow color. It is also found in some lipsticks and has been associated with urticaria and angioedema, she noted.

Food preservatives that have been associated with allergic reactions include butylated hydroxyanisole and sulfites, Dr. Ehrlich said. Sulfites are used to prevent food from turning brown, and it may be present in dried fruit, fruit juice, molasses, pickled foods, vinegar, and wine.

Reports of ACD in response to sodium metabisulfite have been increasing, she noted. Other sulfite reactions may occur with exposure to other products, such as cosmetics, body washes, and swimming pool water, she said.

Awareness of allergens in supplements is important “because the number of our patients taking supplements for different reasons is increasing” and allergens in supplements could account for flares, Dr. Ehrlich said. Clinicians should encourage patients to tell them what supplements they use. Clinicians should review the ingredients in these supplements with their patients to identify potential allergens that may be causing reactions, she advised.

Dr. Ehrlich has disclosed no relevant financial relationships.

A version of this article first appeared on Medscape.com.

Cutaneous Manifestations

Capsicum peppers are used worldwide in preparing spicy dishes. Their active ingredient—capsaicin—is used as a topical medicine to treat localized pain. Capsicum peppers can cause irritant contact dermatitis with symptoms of erythema, cutaneous burning, and itch.¹

Irritant contact dermatitis is a common occupational skin disorder. Many cooks have experienced the sting of a chili pepper after contact with the hands or eyes. Cases of chronic exposure to Capsicum peppers with persistent burning and pain have been called Hunan hand syndrome.²Capsicum peppers also have induced allergic contact dermatitis in a food production worker.³

Capsicum peppers also are used in pepper spray, tear gas, and animal repellents because of their stinging properties. These agents usually cause cutaneous tingling and burning that soon resolves; however, a review of 31 studies showed that crowd-control methods with Capsicum-containing tear gas and pepper spray can cause moderate to severe skin damage such as a persistent skin rash or erythema, or even first-, second-, or third-degree burns.⁴

Topical application of capsaicin isolate is meant to cause burning and deplete local neuropeptides, with a cutaneous reaction that ranges from mild to intolerable.^5,6 Capsaicin also is found in other products. In one published case report, a 3-year-old boy broke out in facial urticaria when his mother kissed him on the cheek after she applied lip plumper containing capsaicin to her lips.⁷ Dermatologists should consider capsaicin an active ingredient that can irritate the skin in the garden, in the kitchen, and in topical products.

Obtaining Relief

Capsaicin-induced dermatitis can be relieved by washing the area with soap, detergent, baking soda, or oily compounds that act as solvents for the nonpolar capsaicin.⁸ Application of ice water or a high-potency topical steroid also may help. If the reaction is severe and persistent, a continuous stellate ganglion block may alleviate the pain of capsaicin-induced contact dermatitis.⁹

Identifying Features and Plant Facts

The Capsicum genus includes chili peppers, paprika, and red peppers. Capsicum peppers are native to tropical regions of the Americas (Figure). The use of Capsicum peppers in food can be traced to Indigenous peoples of Mexico as early as 7000 bc.¹⁰ On the Scoville scale, which was developed to quantify the hotness of foods and spices, Capsicum peppers are rated at approximately 2 million units; by comparison, jalapeño peppers have a Scoville score of 4500¹¹ and capsaicin isolate has a score of 16 million units. Capsicum species rank among the hottest peppers in the world.

Capsicum belongs to the family Solanaceae, which includes tobacco, tomatoes, potatoes, and nightshade plants. There are many varieties of peppers in the Capsicum genus, with 5 domesticated species: Capsicum annuum, Capsicum baccatum, Capsicum chinense, Capsicum frutescens, and Capsicum pubescens. These include bell, poblano, cayenne, tabasco, habanero, and ají peppers, among others. Capsicum species grow as a shrub with flowers that rotate to stellate corollas and rounded berries of different sizes and colors.¹² Capsaicin and other alkaloids are concentrated in the fruit; therefore, Capsicum dermatitis is most commonly induced by contact with the flesh of peppers.

Capsaicin (8-methyl-6-nonanoyl vanillylamide) is a nonpolar phenol, which is why washing skin that has come in contact with capsaicin with water or vinegar alone is insufficient to solubilize it.¹³ Capsaicin binds to the transient receptor potential vanilloid 1 (TRPV1), a calcium channel on neurons that opens in response to heat. When bound, the channel opens at a lower temperature threshold and depolarizes nerve endings, leading to vasodilation and activation of sensory nerves.¹⁴ Substance P is released and the individual experiences a painful burning sensation. When purified capsaicin is frequently applied at an appropriate dose, synthesis of substance P is diminished, resulting in reduced local pain overall.¹⁵

Capsaicin does not affect neurons without TRPV1, and administration of capsaicin is not painful if given with anesthesia. An inappropriately high dose of capsaicin destroys cells in the epidermal barrier, resulting in water loss and inducing release of vasoactive peptides and inflammatory cytokines.¹ Careful handling of Capsicum peppers and capsaicin products can reduce the risk for irritation.

Medicinal Use

On-/Off-Label and Potential Uses—Capsaicin is US Food and Drug Administration approved for use in arthritis and musculoskeletal pain. It also is used to treat diabetic neuropathy,⁵ postherpetic neuralgia,⁶ psoriasis,¹⁶ and other conditions. Studies have shown that capsaicin might be useful in treating trigeminal neuralgia,¹⁷ fibromyalgia,¹⁸ migraines,¹⁴ cluster headaches,⁹ and HIV-associated distal sensory neuropathy.⁵

Delivery of Capsaicin—Capsaicin preferentially acts on C-fibers, which transmit dull, aching, chronic pain.¹⁹ The compound is available as a cream, lotion, and large bandage (for the lower back), as well as low- and high-dose patches. Capsaicin creams, lotions, and the low-dose patch are uncomfortable and must be applied for 4 to 6 weeks to take effect, which may impact patient adherence. The high-dose patch, which requires administration under local anesthesia by a health care worker, brings pain relief with a single use and improves adherence.¹¹ Synthetic TRPV1-agonist injectables based on capsaicin have undergone clinical trials for localized pain (eg, postoperative musculoskeletal pain); many patients experience pain relief, though benefit fades over weeks to months.^20,21

Use in Traditional Medicine—Capsicum peppers have been used to aid digestion and promote healing in gastrointestinal conditions, such as dyspepsia.²² The peppers are a source of important vitamins and minerals, including vitamins A, C, and E; many of the B complex vitamins; and magnesium, calcium, and iron.²³

Use as Cancer Therapy—Studies of the use of capsaicin in treating cancer have produced controversial results. In cell and animal models, capsaicin induces apoptosis through downregulation of the Bcl-2 protein; upregulation of oxidative stress, tribbles-related protein 3 (TRIB3), and caspase-3; and other pathways.^19,24-26 On the other hand, consumption of Capsicum peppers has been associated with cancer of the stomach and gallbladder.²⁷ Capsaicin might have anticarcinogenic properties, but its mechanism of action varies, depending on variables not fully understood.

Final Thoughts

Capsaicin is a neuropeptide-active compound found in Capsicum peppers that has many promising applications for use. However, dermatologists should be aware of the possibility of a skin reaction to this compound from handling peppers and using topical medicines. Exposure to capsaicin can cause irritant contact dermatitis that may require clinical care.

Cutaneous Manifestations

Capsicum peppers are used worldwide in preparing spicy dishes. Their active ingredient—capsaicin—is used as a topical medicine to treat localized pain. Capsicum peppers can cause irritant contact dermatitis with symptoms of erythema, cutaneous burning, and itch.¹

Irritant contact dermatitis is a common occupational skin disorder. Many cooks have experienced the sting of a chili pepper after contact with the hands or eyes. Cases of chronic exposure to Capsicum peppers with persistent burning and pain have been called Hunan hand syndrome.²Capsicum peppers also have induced allergic contact dermatitis in a food production worker.³

Capsicum peppers also are used in pepper spray, tear gas, and animal repellents because of their stinging properties. These agents usually cause cutaneous tingling and burning that soon resolves; however, a review of 31 studies showed that crowd-control methods with Capsicum-containing tear gas and pepper spray can cause moderate to severe skin damage such as a persistent skin rash or erythema, or even first-, second-, or third-degree burns.⁴

Topical application of capsaicin isolate is meant to cause burning and deplete local neuropeptides, with a cutaneous reaction that ranges from mild to intolerable.^5,6 Capsaicin also is found in other products. In one published case report, a 3-year-old boy broke out in facial urticaria when his mother kissed him on the cheek after she applied lip plumper containing capsaicin to her lips.⁷ Dermatologists should consider capsaicin an active ingredient that can irritate the skin in the garden, in the kitchen, and in topical products.

Obtaining Relief

Capsaicin-induced dermatitis can be relieved by washing the area with soap, detergent, baking soda, or oily compounds that act as solvents for the nonpolar capsaicin.⁸ Application of ice water or a high-potency topical steroid also may help. If the reaction is severe and persistent, a continuous stellate ganglion block may alleviate the pain of capsaicin-induced contact dermatitis.⁹

Identifying Features and Plant Facts

The Capsicum genus includes chili peppers, paprika, and red peppers. Capsicum peppers are native to tropical regions of the Americas (Figure). The use of Capsicum peppers in food can be traced to Indigenous peoples of Mexico as early as 7000 bc.¹⁰ On the Scoville scale, which was developed to quantify the hotness of foods and spices, Capsicum peppers are rated at approximately 2 million units; by comparison, jalapeño peppers have a Scoville score of 4500¹¹ and capsaicin isolate has a score of 16 million units. Capsicum species rank among the hottest peppers in the world.

Capsicum belongs to the family Solanaceae, which includes tobacco, tomatoes, potatoes, and nightshade plants. There are many varieties of peppers in the Capsicum genus, with 5 domesticated species: Capsicum annuum, Capsicum baccatum, Capsicum chinense, Capsicum frutescens, and Capsicum pubescens. These include bell, poblano, cayenne, tabasco, habanero, and ají peppers, among others. Capsicum species grow as a shrub with flowers that rotate to stellate corollas and rounded berries of different sizes and colors.¹² Capsaicin and other alkaloids are concentrated in the fruit; therefore, Capsicum dermatitis is most commonly induced by contact with the flesh of peppers.

Capsaicin (8-methyl-6-nonanoyl vanillylamide) is a nonpolar phenol, which is why washing skin that has come in contact with capsaicin with water or vinegar alone is insufficient to solubilize it.¹³ Capsaicin binds to the transient receptor potential vanilloid 1 (TRPV1), a calcium channel on neurons that opens in response to heat. When bound, the channel opens at a lower temperature threshold and depolarizes nerve endings, leading to vasodilation and activation of sensory nerves.¹⁴ Substance P is released and the individual experiences a painful burning sensation. When purified capsaicin is frequently applied at an appropriate dose, synthesis of substance P is diminished, resulting in reduced local pain overall.¹⁵

Capsaicin does not affect neurons without TRPV1, and administration of capsaicin is not painful if given with anesthesia. An inappropriately high dose of capsaicin destroys cells in the epidermal barrier, resulting in water loss and inducing release of vasoactive peptides and inflammatory cytokines.¹ Careful handling of Capsicum peppers and capsaicin products can reduce the risk for irritation.

Medicinal Use

On-/Off-Label and Potential Uses—Capsaicin is US Food and Drug Administration approved for use in arthritis and musculoskeletal pain. It also is used to treat diabetic neuropathy,⁵ postherpetic neuralgia,⁶ psoriasis,¹⁶ and other conditions. Studies have shown that capsaicin might be useful in treating trigeminal neuralgia,¹⁷ fibromyalgia,¹⁸ migraines,¹⁴ cluster headaches,⁹ and HIV-associated distal sensory neuropathy.⁵

Delivery of Capsaicin—Capsaicin preferentially acts on C-fibers, which transmit dull, aching, chronic pain.¹⁹ The compound is available as a cream, lotion, and large bandage (for the lower back), as well as low- and high-dose patches. Capsaicin creams, lotions, and the low-dose patch are uncomfortable and must be applied for 4 to 6 weeks to take effect, which may impact patient adherence. The high-dose patch, which requires administration under local anesthesia by a health care worker, brings pain relief with a single use and improves adherence.¹¹ Synthetic TRPV1-agonist injectables based on capsaicin have undergone clinical trials for localized pain (eg, postoperative musculoskeletal pain); many patients experience pain relief, though benefit fades over weeks to months.^20,21

Use in Traditional Medicine—Capsicum peppers have been used to aid digestion and promote healing in gastrointestinal conditions, such as dyspepsia.²² The peppers are a source of important vitamins and minerals, including vitamins A, C, and E; many of the B complex vitamins; and magnesium, calcium, and iron.²³

Use as Cancer Therapy—Studies of the use of capsaicin in treating cancer have produced controversial results. In cell and animal models, capsaicin induces apoptosis through downregulation of the Bcl-2 protein; upregulation of oxidative stress, tribbles-related protein 3 (TRIB3), and caspase-3; and other pathways.^19,24-26 On the other hand, consumption of Capsicum peppers has been associated with cancer of the stomach and gallbladder.²⁷ Capsaicin might have anticarcinogenic properties, but its mechanism of action varies, depending on variables not fully understood.

Final Thoughts

Capsaicin is a neuropeptide-active compound found in Capsicum peppers that has many promising applications for use. However, dermatologists should be aware of the possibility of a skin reaction to this compound from handling peppers and using topical medicines. Exposure to capsaicin can cause irritant contact dermatitis that may require clinical care.

Cutaneous Manifestations

Capsicum peppers are used worldwide in preparing spicy dishes. Their active ingredient—capsaicin—is used as a topical medicine to treat localized pain. Capsicum peppers can cause irritant contact dermatitis with symptoms of erythema, cutaneous burning, and itch.¹

Irritant contact dermatitis is a common occupational skin disorder. Many cooks have experienced the sting of a chili pepper after contact with the hands or eyes. Cases of chronic exposure to Capsicum peppers with persistent burning and pain have been called Hunan hand syndrome.²Capsicum peppers also have induced allergic contact dermatitis in a food production worker.³

Capsicum peppers also are used in pepper spray, tear gas, and animal repellents because of their stinging properties. These agents usually cause cutaneous tingling and burning that soon resolves; however, a review of 31 studies showed that crowd-control methods with Capsicum-containing tear gas and pepper spray can cause moderate to severe skin damage such as a persistent skin rash or erythema, or even first-, second-, or third-degree burns.⁴

Topical application of capsaicin isolate is meant to cause burning and deplete local neuropeptides, with a cutaneous reaction that ranges from mild to intolerable.^5,6 Capsaicin also is found in other products. In one published case report, a 3-year-old boy broke out in facial urticaria when his mother kissed him on the cheek after she applied lip plumper containing capsaicin to her lips.⁷ Dermatologists should consider capsaicin an active ingredient that can irritate the skin in the garden, in the kitchen, and in topical products.

Obtaining Relief

Capsaicin-induced dermatitis can be relieved by washing the area with soap, detergent, baking soda, or oily compounds that act as solvents for the nonpolar capsaicin.⁸ Application of ice water or a high-potency topical steroid also may help. If the reaction is severe and persistent, a continuous stellate ganglion block may alleviate the pain of capsaicin-induced contact dermatitis.⁹

Identifying Features and Plant Facts

The Capsicum genus includes chili peppers, paprika, and red peppers. Capsicum peppers are native to tropical regions of the Americas (Figure). The use of Capsicum peppers in food can be traced to Indigenous peoples of Mexico as early as 7000 bc.¹⁰ On the Scoville scale, which was developed to quantify the hotness of foods and spices, Capsicum peppers are rated at approximately 2 million units; by comparison, jalapeño peppers have a Scoville score of 4500¹¹ and capsaicin isolate has a score of 16 million units. Capsicum species rank among the hottest peppers in the world.

Capsicum belongs to the family Solanaceae, which includes tobacco, tomatoes, potatoes, and nightshade plants. There are many varieties of peppers in the Capsicum genus, with 5 domesticated species: Capsicum annuum, Capsicum baccatum, Capsicum chinense, Capsicum frutescens, and Capsicum pubescens. These include bell, poblano, cayenne, tabasco, habanero, and ají peppers, among others. Capsicum species grow as a shrub with flowers that rotate to stellate corollas and rounded berries of different sizes and colors.¹² Capsaicin and other alkaloids are concentrated in the fruit; therefore, Capsicum dermatitis is most commonly induced by contact with the flesh of peppers.

Capsaicin (8-methyl-6-nonanoyl vanillylamide) is a nonpolar phenol, which is why washing skin that has come in contact with capsaicin with water or vinegar alone is insufficient to solubilize it.¹³ Capsaicin binds to the transient receptor potential vanilloid 1 (TRPV1), a calcium channel on neurons that opens in response to heat. When bound, the channel opens at a lower temperature threshold and depolarizes nerve endings, leading to vasodilation and activation of sensory nerves.¹⁴ Substance P is released and the individual experiences a painful burning sensation. When purified capsaicin is frequently applied at an appropriate dose, synthesis of substance P is diminished, resulting in reduced local pain overall.¹⁵

Capsaicin does not affect neurons without TRPV1, and administration of capsaicin is not painful if given with anesthesia. An inappropriately high dose of capsaicin destroys cells in the epidermal barrier, resulting in water loss and inducing release of vasoactive peptides and inflammatory cytokines.¹ Careful handling of Capsicum peppers and capsaicin products can reduce the risk for irritation.

Medicinal Use

On-/Off-Label and Potential Uses—Capsaicin is US Food and Drug Administration approved for use in arthritis and musculoskeletal pain. It also is used to treat diabetic neuropathy,⁵ postherpetic neuralgia,⁶ psoriasis,¹⁶ and other conditions. Studies have shown that capsaicin might be useful in treating trigeminal neuralgia,¹⁷ fibromyalgia,¹⁸ migraines,¹⁴ cluster headaches,⁹ and HIV-associated distal sensory neuropathy.⁵

Delivery of Capsaicin—Capsaicin preferentially acts on C-fibers, which transmit dull, aching, chronic pain.¹⁹ The compound is available as a cream, lotion, and large bandage (for the lower back), as well as low- and high-dose patches. Capsaicin creams, lotions, and the low-dose patch are uncomfortable and must be applied for 4 to 6 weeks to take effect, which may impact patient adherence. The high-dose patch, which requires administration under local anesthesia by a health care worker, brings pain relief with a single use and improves adherence.¹¹ Synthetic TRPV1-agonist injectables based on capsaicin have undergone clinical trials for localized pain (eg, postoperative musculoskeletal pain); many patients experience pain relief, though benefit fades over weeks to months.^20,21

Use in Traditional Medicine—Capsicum peppers have been used to aid digestion and promote healing in gastrointestinal conditions, such as dyspepsia.²² The peppers are a source of important vitamins and minerals, including vitamins A, C, and E; many of the B complex vitamins; and magnesium, calcium, and iron.²³

Use as Cancer Therapy—Studies of the use of capsaicin in treating cancer have produced controversial results. In cell and animal models, capsaicin induces apoptosis through downregulation of the Bcl-2 protein; upregulation of oxidative stress, tribbles-related protein 3 (TRIB3), and caspase-3; and other pathways.^19,24-26 On the other hand, consumption of Capsicum peppers has been associated with cancer of the stomach and gallbladder.²⁷ Capsaicin might have anticarcinogenic properties, but its mechanism of action varies, depending on variables not fully understood.

Final Thoughts

Capsaicin is a neuropeptide-active compound found in Capsicum peppers that has many promising applications for use. However, dermatologists should be aware of the possibility of a skin reaction to this compound from handling peppers and using topical medicines. Exposure to capsaicin can cause irritant contact dermatitis that may require clinical care.

Erythema ab igne (EAI)(also known as toasted skin syndrome) was first described in the British Journal of Dermatology in the 20th century, ¹ though it was known by physicians long before. Reticular netlike skin changes were seen in association with patients who spent extended time directly next to a heat source. This association led to the name of this condition, which literally means “redness by fire.” Indeed, EAI induced by chronic heat exposure has been described across the world for centuries. For example, in the cold regions of northern China, people used to sleep on beds of hot bricks called kang to stay warm at night. The people of India’s Kashmir district carried pots of hot coals called kangri next to the skin under large woven shawls to stay warm. In the past, Irish women often spent much time by a turf- or peat-burning fire. Chronic heat exposure in these cases can lead not only to EAI but also to aggressive types of cancer, often with a latency of 30 years or more. ²

More recently, the invention of home central heating led to a stark decrease in the number of cases associated with combustion-based heat, with a transition to etiologies such as use of hot water bottles, electric blankets, and electric space heaters. Over time, technological advances led to ever-increasing potential causes for EAI, such as laptops or cell phones, car heaters and heated seats, heated blankets,^3,4 infrared lamps for food, and even medical devices such as ultrasound-based heating products and convective temperature management systems for hospitalized patients. As technology evolves, so do the potential causes of EAI, requiring clinicians to diagnose and deduce the cause through a thorough social and medical history as well as a workup on the present illness with considerations for the anatomical location.^5-7 Herein, we describe the etiology of EAI, diagnosis, and treatment options.

Clinical Characteristics

Erythema ab igne begins as mild, transient, and erythematous macules and patches in a reticular pattern that resolve minutes to hours after removal of the heat source. With weeks to months of continued or repeated application of the heat source, the affected area eventually becomes hyperpigmented where there once was erythema (Figures 1 and 2). Sometimes papules, bullae, telangiectasia, and hyperkeratosis also form. The rash usually is asymptomatic, though pain, pruritus, and dysesthesia have been reported.⁷ Dermoscopy of EAI in the hyperpigmented stage can reveal diffuse superficial dark pigmentation, telangiectasia, and mild whitish scaling.⁸ Although the pathogenesis has remained elusive over the years, lesions do seem to be mostly associated with cumulative exposure to heat rather than length of exposure.⁷

Etiology of EAI

Anatomic Location—The affected site depends on the source of heat (Table). Classic examples of this condition include a patient with EAI presenting on the anterior thighs after working in front of a hot oven or a patient with chronic back pain presenting with lower-back EAI secondary to frequent use of a hot water bottle or heating pad.⁷ With evolving technology over the last few decades, new etiologies have become more common—teenagers are presenting with anterior thigh EAI secondary to frequent laptop use^2-29; patients are holding warm cell phones in their pant pockets, leading to unilateral geometric EAI on the anterior thigh (front pocket) or buttock (back pocket)³⁰; plug-in radiators under computer desks are causing EAI on the lower legs^31-34; and automobile seat heaters have been shown to cause EAI on the posterior legs.^5,35-37 Clinicians should consider anatomic location a critical clue for etiology.

Social History—There are rarer and more highly specific causes of EAI than simple heat exposure that can be parsed from a patient’s social history. Occupational exposure has been documented, such as bakers with exposure to ovens, foundry workers with exposure to heated metals, or fast-food workers with chronic exposure to infrared food lamps.^6,7 There also are cultural practices that can cause EAI. For example, the practice of cupping with moxibustion was shown to create a specific pattern in the shape of the cultural tool used.³⁸ When footbaths with Chinese herbal remedies are performed frequently with high heat, they can lead to EAI on the feet with a linear border at the ankles. There also have been reports of kotatsu (heated tables in Japan) leading to lower-body EAI.^39,40 These cultural practices also are more common in patients with darker skin types, which can lead to hyperpigmentation that is difficult to treat, making early diagnosis important.⁷

Medical History—Case reports have shown EAI caused by patients attempting to use heat-based methods for pain relief of an underlying serious disease such as cancer, bowel pathology (abdominal EAI), spinal disc prolapse (midline back EAI),⁴¹ sickle cell anemia, and renal pathology (posterior upper flank EAI).^6,7,40-49 Patients with hypothyroidism or anorexia have been noted to have generalized EAI sparing the face secondary to repeated and extended hot baths or showers.^50-53 One patient with schizophrenia was shown to have associated thermophilia due to a delusion that led the patient to soak in hot baths for long periods of time, leading to EAI.⁵⁴ Finally, all physicians should be aware of iatrogenic causes of EAI, such as use of warming devices, ultrasound-based warming techniques, and laser therapy for lipolysis. Inquire about the patient’s surgical history or intensive care unit stays as well as alternative medicine or chiropractic visits. Obtaining a history of medical procedures can be enlightening when an etiology is not immediately clear.^7,55,56

Diagnosis

Erythema ab igne is a clinical diagnosis based on recognizable cutaneous findings and a clear history of moderate heat exposure. However, when a clinical diagnosis of EAI is not certain (eg, when unable to obtain a clear history from the patient) or when malignant transformation is suspected, a biopsy can be performed. Pathologically, hematoxylin and eosin staining of EAI classically reveals dilated small vascular channels in the superficial dermis, hence a clinically reticular rash; interface dermatitis clinically manifesting as erythema; and pigment incontinence with melanin-laden macrophages consistent with clinical hyperpigmentation. Finally, for unclear reasons, increased numbers of elastic fibers classically are seen in biopsies of EAI.⁷

The differential diagnosis for a reticular patch includes livedo reticularis (Figure 3), which usually manifests as a more generalized rash in patients with chronic disease or coagulopathy such as systemic lupus erythematosus, cryoglobulinemia, or Raynaud phenomenon. When differentiating EAI from livedo reticularis or cutis marmorata, consider that both alternative diagnoses are more vascular appearing and are associated with cold exposure rather than heat exposure. In cases that are less reticular, livedo racemosa can be considered in the differential diagnosis. Finally, poikiloderma of Civatte can be reticular, particularly on dermoscopy, but the distribution on the neck with submental sparing should help to distinguish it from EAI unless a heat source around the neck is identified while taking the patient’s history.⁷

In babies, a reticular generalized rash is most likely to be cutis marmorata (Figure 4), which is a physiologic response to cold exposure that resolves with rewarming of the skin. A more serious condition—cutis marmorata telangiectatica congenita (Figure 5)—usually is present at birth, most frequently involves a single extremity, and notably does not resolve with rewarming. This is an important differential for EAI in children because it can be associated with vascular and neurologic anomalies as well as limb asymmetry. Finally, port-wine stains can sometimes be reticular in appearance and can mimic the early erythematous stages of EAI. However, unlike the erythematous stage of EAI, the port-wine stains will be present at birth.⁷

Emerging in 2020, an important differential diagnosis to consider is a cutaneous manifestation of COVID-19 infection. An erythematous, reticular, chilblainlike or transient livedo reticularis–like rash has been described as a cutaneous manifestation of COVID-19. Although the pathophysiology is still being elucidated, it is suspected that this is caused by a major vaso-occlusive crisis secondary to COVID-19–induced thrombotic vasculopathy. Interestingly, the majority of patients with this COVID-related exanthem also displayed symptoms of COVID-19 (eg, fever, cough) at the time of presentation,^57-60 but there also have been cases in patients who were asymptomatic or mildly symptomatic.⁶⁰

In some cases, EAI is an indication to screen for an underlying disease. For example, uncontrolled pain is an opportunity to improve interventions such as modifying the patient’s pain-control regimen, placing a palliative care pain consultation, or checking if the patient has had age-appropriate screenings for malignancy. New focal pain in a patient with a prior diagnosis of cancer may be a sign of a new metastasis. A thermophilic patient leaves opportunity to assess for underlying medical causes such as thyroid abnormalities or social/psychological issues. Geriatric patients who are diagnosed with EAI may need to be assessed for dementia or home safety issues. Patients with a history of diabetes mellitus can unknowingly develop EAI on the lower extremities, which may signal a need to assess the patient for peripheral neuropathy. Patients with gastroparesis secondary to diabetes also may develop EAI on the abdomen secondary to heating pad use for discomfort. These examples are a reminder to consider possible secondary comorbidities in all diagnoses of EAI.⁷ 

Prognosis

Although the prognosis of EAI is excellent if caught early, failure to diagnose this condition can lead to permanent discoloration of the skin and even malignancy.⁶ A rare sequela includes squamous cell carcinoma, most commonly seen in chronic cases of the lower leg, which is likely related to chronic inflammation of the skin.^61-65 Rare cases of poorly differentiated carcinoma,⁶⁶ cutaneous marginal zone lymphoma,⁶⁷ and Merkel cell carcinoma⁶⁸ have been reported. Patients diagnosed with EAI should receive normal periodic surveillance of the skin based on their medical history, though the physician should have an increased suspicion and plan for biopsy of any nodules or ulcerations found on the skin of the affected area.⁷

Treatments

Once the diagnosis of EAI is made, treatment starts with removal of the heat source causing the rash. Because the rash usually is asymptomatic, further treatment typically is not required. The discoloration can resolve over months or years, but permanent hyperpigmentation is not uncommon. If hyperpigmentation persists despite removal of the heat source and the patient desires further treatment for discoloration, there are few treatment options, none of which are approved by the US Food and Drug Administration for this condition.⁷ There is some evidence for the use of Nd:YAG lasers to reduce hyperpigmentation in EAI.⁶⁹ There have been some reports of treatment using topical hydroquinone and topical tretinoin in an attempt to lighten the skin. If associated hyperkeratosis or other epithelial atypia is present, the use of 5-fluorouracil may show some improvement.⁷⁰ One case report has been published of successful treatment with systemic mesoglycan and topical bioflavonoids.⁷¹ It also is conceivable that medications used to treat postinflammatory hyperpigmentation may be helpful in this condition (eg, kojic acid, arbutin, mild topical steroids, azelaic acid). Patients with darker skin may experience permanent discoloration and may not be good candidates for alternative treatments such as laser therapy due to the risk for inducible hyperpigmentation.⁷

Conclusion

No matter the etiology, EAI usually is a benign skin condition that is treated by removal of the causative heat source. Once a diagnosis is made, the clinician must work with the patient to determine the etiology. Care must be taken to ensure that there are no underlying signs, such as chronic pain or psychiatric illness, that could point to associated conditions. Rarely, sequalae such as cancers have been documented in areas of chronic EAI. Once the heat source is identified and removed, any remaining hyperpigmentation usually will self-resolve over months to years, though this may take longer in patients with darker skin types. If more aggressive treatment is preferred by the patient, laser therapy, topical medications, and oral over-the-counter vitamins have been tried with minimal responses. 

Erythema ab igne (EAI)(also known as toasted skin syndrome) was first described in the British Journal of Dermatology in the 20th century, ¹ though it was known by physicians long before. Reticular netlike skin changes were seen in association with patients who spent extended time directly next to a heat source. This association led to the name of this condition, which literally means “redness by fire.” Indeed, EAI induced by chronic heat exposure has been described across the world for centuries. For example, in the cold regions of northern China, people used to sleep on beds of hot bricks called kang to stay warm at night. The people of India’s Kashmir district carried pots of hot coals called kangri next to the skin under large woven shawls to stay warm. In the past, Irish women often spent much time by a turf- or peat-burning fire. Chronic heat exposure in these cases can lead not only to EAI but also to aggressive types of cancer, often with a latency of 30 years or more. ²

More recently, the invention of home central heating led to a stark decrease in the number of cases associated with combustion-based heat, with a transition to etiologies such as use of hot water bottles, electric blankets, and electric space heaters. Over time, technological advances led to ever-increasing potential causes for EAI, such as laptops or cell phones, car heaters and heated seats, heated blankets,^3,4 infrared lamps for food, and even medical devices such as ultrasound-based heating products and convective temperature management systems for hospitalized patients. As technology evolves, so do the potential causes of EAI, requiring clinicians to diagnose and deduce the cause through a thorough social and medical history as well as a workup on the present illness with considerations for the anatomical location.^5-7 Herein, we describe the etiology of EAI, diagnosis, and treatment options.

Clinical Characteristics

Erythema ab igne begins as mild, transient, and erythematous macules and patches in a reticular pattern that resolve minutes to hours after removal of the heat source. With weeks to months of continued or repeated application of the heat source, the affected area eventually becomes hyperpigmented where there once was erythema (Figures 1 and 2). Sometimes papules, bullae, telangiectasia, and hyperkeratosis also form. The rash usually is asymptomatic, though pain, pruritus, and dysesthesia have been reported.⁷ Dermoscopy of EAI in the hyperpigmented stage can reveal diffuse superficial dark pigmentation, telangiectasia, and mild whitish scaling.⁸ Although the pathogenesis has remained elusive over the years, lesions do seem to be mostly associated with cumulative exposure to heat rather than length of exposure.⁷

Etiology of EAI

Anatomic Location—The affected site depends on the source of heat (Table). Classic examples of this condition include a patient with EAI presenting on the anterior thighs after working in front of a hot oven or a patient with chronic back pain presenting with lower-back EAI secondary to frequent use of a hot water bottle or heating pad.⁷ With evolving technology over the last few decades, new etiologies have become more common—teenagers are presenting with anterior thigh EAI secondary to frequent laptop use^2-29; patients are holding warm cell phones in their pant pockets, leading to unilateral geometric EAI on the anterior thigh (front pocket) or buttock (back pocket)³⁰; plug-in radiators under computer desks are causing EAI on the lower legs^31-34; and automobile seat heaters have been shown to cause EAI on the posterior legs.^5,35-37 Clinicians should consider anatomic location a critical clue for etiology.

Social History—There are rarer and more highly specific causes of EAI than simple heat exposure that can be parsed from a patient’s social history. Occupational exposure has been documented, such as bakers with exposure to ovens, foundry workers with exposure to heated metals, or fast-food workers with chronic exposure to infrared food lamps.^6,7 There also are cultural practices that can cause EAI. For example, the practice of cupping with moxibustion was shown to create a specific pattern in the shape of the cultural tool used.³⁸ When footbaths with Chinese herbal remedies are performed frequently with high heat, they can lead to EAI on the feet with a linear border at the ankles. There also have been reports of kotatsu (heated tables in Japan) leading to lower-body EAI.^39,40 These cultural practices also are more common in patients with darker skin types, which can lead to hyperpigmentation that is difficult to treat, making early diagnosis important.⁷

Medical History—Case reports have shown EAI caused by patients attempting to use heat-based methods for pain relief of an underlying serious disease such as cancer, bowel pathology (abdominal EAI), spinal disc prolapse (midline back EAI),⁴¹ sickle cell anemia, and renal pathology (posterior upper flank EAI).^6,7,40-49 Patients with hypothyroidism or anorexia have been noted to have generalized EAI sparing the face secondary to repeated and extended hot baths or showers.^50-53 One patient with schizophrenia was shown to have associated thermophilia due to a delusion that led the patient to soak in hot baths for long periods of time, leading to EAI.⁵⁴ Finally, all physicians should be aware of iatrogenic causes of EAI, such as use of warming devices, ultrasound-based warming techniques, and laser therapy for lipolysis. Inquire about the patient’s surgical history or intensive care unit stays as well as alternative medicine or chiropractic visits. Obtaining a history of medical procedures can be enlightening when an etiology is not immediately clear.^7,55,56

Diagnosis

Erythema ab igne is a clinical diagnosis based on recognizable cutaneous findings and a clear history of moderate heat exposure. However, when a clinical diagnosis of EAI is not certain (eg, when unable to obtain a clear history from the patient) or when malignant transformation is suspected, a biopsy can be performed. Pathologically, hematoxylin and eosin staining of EAI classically reveals dilated small vascular channels in the superficial dermis, hence a clinically reticular rash; interface dermatitis clinically manifesting as erythema; and pigment incontinence with melanin-laden macrophages consistent with clinical hyperpigmentation. Finally, for unclear reasons, increased numbers of elastic fibers classically are seen in biopsies of EAI.⁷

The differential diagnosis for a reticular patch includes livedo reticularis (Figure 3), which usually manifests as a more generalized rash in patients with chronic disease or coagulopathy such as systemic lupus erythematosus, cryoglobulinemia, or Raynaud phenomenon. When differentiating EAI from livedo reticularis or cutis marmorata, consider that both alternative diagnoses are more vascular appearing and are associated with cold exposure rather than heat exposure. In cases that are less reticular, livedo racemosa can be considered in the differential diagnosis. Finally, poikiloderma of Civatte can be reticular, particularly on dermoscopy, but the distribution on the neck with submental sparing should help to distinguish it from EAI unless a heat source around the neck is identified while taking the patient’s history.⁷

In babies, a reticular generalized rash is most likely to be cutis marmorata (Figure 4), which is a physiologic response to cold exposure that resolves with rewarming of the skin. A more serious condition—cutis marmorata telangiectatica congenita (Figure 5)—usually is present at birth, most frequently involves a single extremity, and notably does not resolve with rewarming. This is an important differential for EAI in children because it can be associated with vascular and neurologic anomalies as well as limb asymmetry. Finally, port-wine stains can sometimes be reticular in appearance and can mimic the early erythematous stages of EAI. However, unlike the erythematous stage of EAI, the port-wine stains will be present at birth.⁷

Emerging in 2020, an important differential diagnosis to consider is a cutaneous manifestation of COVID-19 infection. An erythematous, reticular, chilblainlike or transient livedo reticularis–like rash has been described as a cutaneous manifestation of COVID-19. Although the pathophysiology is still being elucidated, it is suspected that this is caused by a major vaso-occlusive crisis secondary to COVID-19–induced thrombotic vasculopathy. Interestingly, the majority of patients with this COVID-related exanthem also displayed symptoms of COVID-19 (eg, fever, cough) at the time of presentation,^57-60 but there also have been cases in patients who were asymptomatic or mildly symptomatic.⁶⁰

In some cases, EAI is an indication to screen for an underlying disease. For example, uncontrolled pain is an opportunity to improve interventions such as modifying the patient’s pain-control regimen, placing a palliative care pain consultation, or checking if the patient has had age-appropriate screenings for malignancy. New focal pain in a patient with a prior diagnosis of cancer may be a sign of a new metastasis. A thermophilic patient leaves opportunity to assess for underlying medical causes such as thyroid abnormalities or social/psychological issues. Geriatric patients who are diagnosed with EAI may need to be assessed for dementia or home safety issues. Patients with a history of diabetes mellitus can unknowingly develop EAI on the lower extremities, which may signal a need to assess the patient for peripheral neuropathy. Patients with gastroparesis secondary to diabetes also may develop EAI on the abdomen secondary to heating pad use for discomfort. These examples are a reminder to consider possible secondary comorbidities in all diagnoses of EAI.⁷ 

Prognosis

Although the prognosis of EAI is excellent if caught early, failure to diagnose this condition can lead to permanent discoloration of the skin and even malignancy.⁶ A rare sequela includes squamous cell carcinoma, most commonly seen in chronic cases of the lower leg, which is likely related to chronic inflammation of the skin.^61-65 Rare cases of poorly differentiated carcinoma,⁶⁶ cutaneous marginal zone lymphoma,⁶⁷ and Merkel cell carcinoma⁶⁸ have been reported. Patients diagnosed with EAI should receive normal periodic surveillance of the skin based on their medical history, though the physician should have an increased suspicion and plan for biopsy of any nodules or ulcerations found on the skin of the affected area.⁷

Treatments

Once the diagnosis of EAI is made, treatment starts with removal of the heat source causing the rash. Because the rash usually is asymptomatic, further treatment typically is not required. The discoloration can resolve over months or years, but permanent hyperpigmentation is not uncommon. If hyperpigmentation persists despite removal of the heat source and the patient desires further treatment for discoloration, there are few treatment options, none of which are approved by the US Food and Drug Administration for this condition.⁷ There is some evidence for the use of Nd:YAG lasers to reduce hyperpigmentation in EAI.⁶⁹ There have been some reports of treatment using topical hydroquinone and topical tretinoin in an attempt to lighten the skin. If associated hyperkeratosis or other epithelial atypia is present, the use of 5-fluorouracil may show some improvement.⁷⁰ One case report has been published of successful treatment with systemic mesoglycan and topical bioflavonoids.⁷¹ It also is conceivable that medications used to treat postinflammatory hyperpigmentation may be helpful in this condition (eg, kojic acid, arbutin, mild topical steroids, azelaic acid). Patients with darker skin may experience permanent discoloration and may not be good candidates for alternative treatments such as laser therapy due to the risk for inducible hyperpigmentation.⁷

Conclusion

No matter the etiology, EAI usually is a benign skin condition that is treated by removal of the causative heat source. Once a diagnosis is made, the clinician must work with the patient to determine the etiology. Care must be taken to ensure that there are no underlying signs, such as chronic pain or psychiatric illness, that could point to associated conditions. Rarely, sequalae such as cancers have been documented in areas of chronic EAI. Once the heat source is identified and removed, any remaining hyperpigmentation usually will self-resolve over months to years, though this may take longer in patients with darker skin types. If more aggressive treatment is preferred by the patient, laser therapy, topical medications, and oral over-the-counter vitamins have been tried with minimal responses. 

Erythema ab igne (EAI)(also known as toasted skin syndrome) was first described in the British Journal of Dermatology in the 20th century, ¹ though it was known by physicians long before. Reticular netlike skin changes were seen in association with patients who spent extended time directly next to a heat source. This association led to the name of this condition, which literally means “redness by fire.” Indeed, EAI induced by chronic heat exposure has been described across the world for centuries. For example, in the cold regions of northern China, people used to sleep on beds of hot bricks called kang to stay warm at night. The people of India’s Kashmir district carried pots of hot coals called kangri next to the skin under large woven shawls to stay warm. In the past, Irish women often spent much time by a turf- or peat-burning fire. Chronic heat exposure in these cases can lead not only to EAI but also to aggressive types of cancer, often with a latency of 30 years or more. ²

More recently, the invention of home central heating led to a stark decrease in the number of cases associated with combustion-based heat, with a transition to etiologies such as use of hot water bottles, electric blankets, and electric space heaters. Over time, technological advances led to ever-increasing potential causes for EAI, such as laptops or cell phones, car heaters and heated seats, heated blankets,^3,4 infrared lamps for food, and even medical devices such as ultrasound-based heating products and convective temperature management systems for hospitalized patients. As technology evolves, so do the potential causes of EAI, requiring clinicians to diagnose and deduce the cause through a thorough social and medical history as well as a workup on the present illness with considerations for the anatomical location.^5-7 Herein, we describe the etiology of EAI, diagnosis, and treatment options.

Clinical Characteristics

Erythema ab igne begins as mild, transient, and erythematous macules and patches in a reticular pattern that resolve minutes to hours after removal of the heat source. With weeks to months of continued or repeated application of the heat source, the affected area eventually becomes hyperpigmented where there once was erythema (Figures 1 and 2). Sometimes papules, bullae, telangiectasia, and hyperkeratosis also form. The rash usually is asymptomatic, though pain, pruritus, and dysesthesia have been reported.⁷ Dermoscopy of EAI in the hyperpigmented stage can reveal diffuse superficial dark pigmentation, telangiectasia, and mild whitish scaling.⁸ Although the pathogenesis has remained elusive over the years, lesions do seem to be mostly associated with cumulative exposure to heat rather than length of exposure.⁷

Etiology of EAI

Anatomic Location—The affected site depends on the source of heat (Table). Classic examples of this condition include a patient with EAI presenting on the anterior thighs after working in front of a hot oven or a patient with chronic back pain presenting with lower-back EAI secondary to frequent use of a hot water bottle or heating pad.⁷ With evolving technology over the last few decades, new etiologies have become more common—teenagers are presenting with anterior thigh EAI secondary to frequent laptop use^2-29; patients are holding warm cell phones in their pant pockets, leading to unilateral geometric EAI on the anterior thigh (front pocket) or buttock (back pocket)³⁰; plug-in radiators under computer desks are causing EAI on the lower legs^31-34; and automobile seat heaters have been shown to cause EAI on the posterior legs.^5,35-37 Clinicians should consider anatomic location a critical clue for etiology.

Social History—There are rarer and more highly specific causes of EAI than simple heat exposure that can be parsed from a patient’s social history. Occupational exposure has been documented, such as bakers with exposure to ovens, foundry workers with exposure to heated metals, or fast-food workers with chronic exposure to infrared food lamps.^6,7 There also are cultural practices that can cause EAI. For example, the practice of cupping with moxibustion was shown to create a specific pattern in the shape of the cultural tool used.³⁸ When footbaths with Chinese herbal remedies are performed frequently with high heat, they can lead to EAI on the feet with a linear border at the ankles. There also have been reports of kotatsu (heated tables in Japan) leading to lower-body EAI.^39,40 These cultural practices also are more common in patients with darker skin types, which can lead to hyperpigmentation that is difficult to treat, making early diagnosis important.⁷

Medical History—Case reports have shown EAI caused by patients attempting to use heat-based methods for pain relief of an underlying serious disease such as cancer, bowel pathology (abdominal EAI), spinal disc prolapse (midline back EAI),⁴¹ sickle cell anemia, and renal pathology (posterior upper flank EAI).^6,7,40-49 Patients with hypothyroidism or anorexia have been noted to have generalized EAI sparing the face secondary to repeated and extended hot baths or showers.^50-53 One patient with schizophrenia was shown to have associated thermophilia due to a delusion that led the patient to soak in hot baths for long periods of time, leading to EAI.⁵⁴ Finally, all physicians should be aware of iatrogenic causes of EAI, such as use of warming devices, ultrasound-based warming techniques, and laser therapy for lipolysis. Inquire about the patient’s surgical history or intensive care unit stays as well as alternative medicine or chiropractic visits. Obtaining a history of medical procedures can be enlightening when an etiology is not immediately clear.^7,55,56

Diagnosis

Erythema ab igne is a clinical diagnosis based on recognizable cutaneous findings and a clear history of moderate heat exposure. However, when a clinical diagnosis of EAI is not certain (eg, when unable to obtain a clear history from the patient) or when malignant transformation is suspected, a biopsy can be performed. Pathologically, hematoxylin and eosin staining of EAI classically reveals dilated small vascular channels in the superficial dermis, hence a clinically reticular rash; interface dermatitis clinically manifesting as erythema; and pigment incontinence with melanin-laden macrophages consistent with clinical hyperpigmentation. Finally, for unclear reasons, increased numbers of elastic fibers classically are seen in biopsies of EAI.⁷

The differential diagnosis for a reticular patch includes livedo reticularis (Figure 3), which usually manifests as a more generalized rash in patients with chronic disease or coagulopathy such as systemic lupus erythematosus, cryoglobulinemia, or Raynaud phenomenon. When differentiating EAI from livedo reticularis or cutis marmorata, consider that both alternative diagnoses are more vascular appearing and are associated with cold exposure rather than heat exposure. In cases that are less reticular, livedo racemosa can be considered in the differential diagnosis. Finally, poikiloderma of Civatte can be reticular, particularly on dermoscopy, but the distribution on the neck with submental sparing should help to distinguish it from EAI unless a heat source around the neck is identified while taking the patient’s history.⁷

In babies, a reticular generalized rash is most likely to be cutis marmorata (Figure 4), which is a physiologic response to cold exposure that resolves with rewarming of the skin. A more serious condition—cutis marmorata telangiectatica congenita (Figure 5)—usually is present at birth, most frequently involves a single extremity, and notably does not resolve with rewarming. This is an important differential for EAI in children because it can be associated with vascular and neurologic anomalies as well as limb asymmetry. Finally, port-wine stains can sometimes be reticular in appearance and can mimic the early erythematous stages of EAI. However, unlike the erythematous stage of EAI, the port-wine stains will be present at birth.⁷

Emerging in 2020, an important differential diagnosis to consider is a cutaneous manifestation of COVID-19 infection. An erythematous, reticular, chilblainlike or transient livedo reticularis–like rash has been described as a cutaneous manifestation of COVID-19. Although the pathophysiology is still being elucidated, it is suspected that this is caused by a major vaso-occlusive crisis secondary to COVID-19–induced thrombotic vasculopathy. Interestingly, the majority of patients with this COVID-related exanthem also displayed symptoms of COVID-19 (eg, fever, cough) at the time of presentation,^57-60 but there also have been cases in patients who were asymptomatic or mildly symptomatic.⁶⁰

In some cases, EAI is an indication to screen for an underlying disease. For example, uncontrolled pain is an opportunity to improve interventions such as modifying the patient’s pain-control regimen, placing a palliative care pain consultation, or checking if the patient has had age-appropriate screenings for malignancy. New focal pain in a patient with a prior diagnosis of cancer may be a sign of a new metastasis. A thermophilic patient leaves opportunity to assess for underlying medical causes such as thyroid abnormalities or social/psychological issues. Geriatric patients who are diagnosed with EAI may need to be assessed for dementia or home safety issues. Patients with a history of diabetes mellitus can unknowingly develop EAI on the lower extremities, which may signal a need to assess the patient for peripheral neuropathy. Patients with gastroparesis secondary to diabetes also may develop EAI on the abdomen secondary to heating pad use for discomfort. These examples are a reminder to consider possible secondary comorbidities in all diagnoses of EAI.⁷ 

Prognosis

Although the prognosis of EAI is excellent if caught early, failure to diagnose this condition can lead to permanent discoloration of the skin and even malignancy.⁶ A rare sequela includes squamous cell carcinoma, most commonly seen in chronic cases of the lower leg, which is likely related to chronic inflammation of the skin.^61-65 Rare cases of poorly differentiated carcinoma,⁶⁶ cutaneous marginal zone lymphoma,⁶⁷ and Merkel cell carcinoma⁶⁸ have been reported. Patients diagnosed with EAI should receive normal periodic surveillance of the skin based on their medical history, though the physician should have an increased suspicion and plan for biopsy of any nodules or ulcerations found on the skin of the affected area.⁷

Treatments

Once the diagnosis of EAI is made, treatment starts with removal of the heat source causing the rash. Because the rash usually is asymptomatic, further treatment typically is not required. The discoloration can resolve over months or years, but permanent hyperpigmentation is not uncommon. If hyperpigmentation persists despite removal of the heat source and the patient desires further treatment for discoloration, there are few treatment options, none of which are approved by the US Food and Drug Administration for this condition.⁷ There is some evidence for the use of Nd:YAG lasers to reduce hyperpigmentation in EAI.⁶⁹ There have been some reports of treatment using topical hydroquinone and topical tretinoin in an attempt to lighten the skin. If associated hyperkeratosis or other epithelial atypia is present, the use of 5-fluorouracil may show some improvement.⁷⁰ One case report has been published of successful treatment with systemic mesoglycan and topical bioflavonoids.⁷¹ It also is conceivable that medications used to treat postinflammatory hyperpigmentation may be helpful in this condition (eg, kojic acid, arbutin, mild topical steroids, azelaic acid). Patients with darker skin may experience permanent discoloration and may not be good candidates for alternative treatments such as laser therapy due to the risk for inducible hyperpigmentation.⁷

Conclusion

No matter the etiology, EAI usually is a benign skin condition that is treated by removal of the causative heat source. Once a diagnosis is made, the clinician must work with the patient to determine the etiology. Care must be taken to ensure that there are no underlying signs, such as chronic pain or psychiatric illness, that could point to associated conditions. Rarely, sequalae such as cancers have been documented in areas of chronic EAI. Once the heat source is identified and removed, any remaining hyperpigmentation usually will self-resolve over months to years, though this may take longer in patients with darker skin types. If more aggressive treatment is preferred by the patient, laser therapy, topical medications, and oral over-the-counter vitamins have been tried with minimal responses. 

Laundry detergent, a cleaning agent ubiquitous in the modern household, often is suspected as a cause of allergic contact dermatitis (ACD). In one North American study, 10.7% of 738 patients undergoing patch testing believed that laundry detergent was a contributing factor, whereas their referring physicians had the same concern less often (in 2.3% of cases).¹Likewise, in a 1992 survey of western US households, more than 20% of 3841 respondents reported skin or health problems attributed to a textile and/or laundry product.² The suspicion of laundry detergent as a causative agent of ACD is perpetuated across popular wellness and beauty websites.^3,4 Does the evidence support this degree of suspicion? Or, similar to the well-meaning parent who misguidedly fixates on foods as the cause of their child’s atopic dermatitis and believes elimination diets are the solution,⁵ could a similar desire for control in the face of the unpredictability of eczema drive consumers and health care providers alike to blame laundry detergent—a familiar and modifiable cause?

We provide a summary of the evidence for the potential allergenicity of laundry detergent, including common allergens present in laundry detergent, the role of machine washing, and the differential diagnosis for laundry detergent–associated ACD.

Allergenic Ingredients in Laundry Detergent

Potential allergens present in laundry detergent include fragrances, preservatives, surfactants, emulsifiers, bleaches, brighteners, enzymes, and dyes.^6-8 In an analysis of allergens present in laundry detergents available in the United States, fragrances and preservatives were most common (eTable).^7,8 Contact allergy to fragrances occurs in approximately 3.5% of the general population⁹ and is detected in as many as 9.2% of patients referred for patch testing in North America.¹⁰ Preservatives commonly found in laundry detergent include isothiazolinones, such as methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI), MI alone, and benzisothiazolinone (BIT). Methylisothiazolinone has gained attention for causing an ACD epidemic beginning in the early 2000s and peaking in Europe between 2013 and 2014 and decreasing thereafter due to consumer personal care product regulatory changes enacted in the European Union.¹¹ In contrast, rates of MI allergy in North America have continued to increase (reaching as high as 15% of patch tested patients in 2017-2018) due to a lack of similar regulation.^10,12 More recently, the prevalence of positive patch tests to BIT has been rising, though it often is difficult to ascertain relevant sources of exposure, and some cases could represent cross-reactions to MCI/MI.^10,13

Other allergens that may be present in laundry detergent include surfactants and propylene glycol. Alkyl glucosides such as decyl glucoside and lauryl glucoside are considered gentle surfactants and often are included in products marketed as safe for sensitive skin,¹⁴ such as “free and gentle” detergents.⁸ However, they actually may pose an increased risk for sensitization in patients with atopic dermatitis.¹⁴ In addition to being allergenic, surfactants and emulsifiers are known irritants.^6,15 Although pathologically distinct, ACD and irritant contact dermatitis can be indistinguishable on clinical presentation.

How Commonly Does Laundry Detergent Cause ACD?

The mere presence of a contact allergen in laundry detergent does not necessarily imply that it is likely to cause ACD. To do so, the chemical in question must exceed the exposure thresholds for primary sensitization (ie, induction of contact allergy) and/or elicitation (ie, development of ACD in sensitized individuals). These depend on a complex interplay of product- and patient-specific factors, among them the concentration of the chemical in the detergent, the method of use, and the amount of detergent residue remaining on clothing after washing.

In the 1990s, the North American Contact Dermatitis Group (NACDG) attempted to determine the prevalence of ACD caused by laundry detergent.¹ Among 738 patients patch tested to aqueous dilutions of granular and liquid laundry detergents, only 5 (0.7%) had a possible allergic patch test reaction. It was unclear what the culprit allergens in the detergents may have been; only 1 of the patients also tested positive to fragrance. Two patients underwent further testing to additional detergent dilutions, and the results called into question whether their initial reactions had truly been allergic (positive) or were actually irritant (negative). The investigators concluded that the prevalence of laundry detergent–associated ACD in this large group of patients was at most 0.7%, and possibly lower.¹

Importantly, patch testing to laundry detergents should not be undertaken in routine clinical practice. Laundry detergents should never be tested “as is” (ie, undiluted) on the skin; they are inherently irritating and have a high likelihood of producing misleading false-positive reactions. Careful dilutions and testing of control subjects are necessary if patch testing with these products is to be appropriately conducted.

The extremely low prevalence of laundry detergent–associated ACD reported by the NACDG was determined prior to the start of the worldwide MI allergy epidemic, raising the possibility that laundry detergents containing isothiazolinones may be associated with ACD. There is no consensus about the minimum level at which isothiazolinones pose no risk to consumers,^16-19 but the US Expert Panel for Cosmetic Ingredient Safety declared that MI is “safe for use in rinse-off cosmetic products at concentrations up to 100 ppm and safe in leave-on cosmetic products when they are formulated to be nonsensitizing.”^18,19 Although ingredient lists do not always reveal when isothiazolinones are present, analyses of commercially available laundry detergents have shown MI concentrations ranging from undetectable to 65.7 ppm.^20-23

Published reports suggest that MCI/MI in laundry detergent can elicit ACD in sensitized individuals. In one case, a 7-year-old girl with chronic truncal dermatitis (atopic history unspecified) was patch tested, revealing a strongly positive reaction to MCI/MI.²⁴ Her laundry detergent was the only personal product found to contain MI. The dermatitis completely resolved after switching detergents and flared after wearing a jacket that had been washed in the implicated detergent, further supporting the relevance of the positive patch test. The investigators suspected initial sensitization to MI from wet wipes used earlier in childhood.²⁴ In another case involving occupational exposure, a 39-year-old nonatopic factory worker was responsible for directly adding MI to laundry detergent.²⁵ Although he wore disposable work gloves, he developed severe hand dermatitis, eczematous pretibial patches, and generalized pruritus. Patch testing revealed positive reactions to MCI/MI and MI, and he experienced improvement when reassigned to different work duties. It was hypothesized that the leg dermatitis and generalized pruritus may have been related to exposure to small concentrations of MI in work clothes washed with an MI-containing detergent.²⁵ Notably, this patient’s level of exposure was much greater than that encountered by individuals in day-to-day life outside of specialized occupational settings.

Regarding other isothiazolinones, a toxicologic study estimated that BIT in laundry detergent would be unlikely to induce sensitization, even at the maximal acceptable concentration, as recommended by preservative manufacturers, and accounting for undiluted detergent spilling directly onto the skin.²⁶Nonetheless, a single European center recently reported that almost half of the 38 patients with positive patch tests to BIT had a potentially relevant exposure attributed to household cleaning products, including laundry detergent.¹³ This emphasizes the need for further examination of sources of exposure to this increasingly common positive patch test allergen.

Does Machine Washing Impact Allergen Concentrations?

Two recent investigations have suggested that machine washing reduces concentrations of isothiazolinones to levels that are likely below clinical relevance. In the first study, 3 fabrics—cotton, polyester, cotton-polyester—were machine washed and line dried.²⁷ A standard detergent was used with MI added at different concentrations: less than 1 ppm, 100 ppm, and 1000 ppm. This process was either performed once or 10 times. Following laundering and line drying, MI was undetectable in all fabrics regardless of MI concentration or number of times washed (detection limit, 0.5 ppm).²⁷ In the second study, 4 fabrics—cotton, wool, polyester, linen—were washed with standard laundry detergent in 1 of 4 ways: handwashing (positive control), standard machine washing, standard machine washing with fabric softener, and standard machine washing with a double rinse.²⁸ After laundering and line drying, concentrations of MI, MCI, and BIT were low or undetectable regardless of fabric type or method of laundering. The highest levels detected were in handwashed garments at a maximum of 0.5 ppm of MI. The study authors postulated that chemical concentrations near these maximum residual levels may pose a risk for eliciting ACD in highly sensitized individuals. Therefore, handwashing can be considered a much higher risk activity for isothiazolinone ACD compared with machine washing.²⁸

It is intriguing that machine washing appears to reduce isothiazolinones to low concentrations that may have limited likelihood of causing ACD. Similar findings have been reported regarding fragrances. A quantitative risk assessment performed on 24 of 26 fragrance allergens regulated by the European Union determined that the amount of fragrance deposited on the skin from laundered garments would be less than the threshold for causing sensitization.²⁹ Although this risk assessment was unable to address the threshold of elicitation, another study conducted in Europe investigated whether fragrance residues present on fabric, such as those deposited from laundry detergent, are present at high enough concentrations to elicit ACD in previously sensitized individuals.³⁰ When 36 individuals were patch tested with increasing concentrations of a fragrance to which they were already sensitized, only 2 (5.6%) had a weakly positive reaction and then only to the highest concentration, which was estimated to be 20-fold higher than the level of skin exposure after normal laundering. No patient reacted at lower concentrations.³⁰

Although machine washing may decrease isothiazolinone and/or fragrance concentrations in laundry detergent to below clinically relevant levels, these findings should not necessarily be extrapolated to all chemicals in laundry detergent. Indeed, a prior study observed that after washing cotton cloths in a detergent solution for 10 minutes, detergent residue was present at concentrations ranging from 139 to 2820 ppm and required a subsequent 20 to 22 washes in water to become undetectable.³¹ Another study produced a mathematical model of the residual concentration of sodium dodecyl sulphate (SDS), a surfactant and known irritant, in laundered clothing.³² It was estimated that after machine washing, the residual concentration of SDS on clothes would be too low to cause irritation; however, as the clothes dry (ie, as moisture evaporates but solutes remain), the concentration of SDS on the fabric’s surface would increase to potentially irritating levels. The extensive drying that is possible with electric dryers may further enhance this solute-concentrating effect.

Differential Diagnosis of Laundry Detergent ACD

The propensity for laundry detergent to cause ACD is a question that is nowhere near settled, but the prevalence of allergy likely is far less common than is generally suspected. In our experience, many patients presenting for patch testing have already made the change to “free and clear” detergents without noticeable improvement in their dermatitis, which could possibly relate to the ongoing presence of contact allergens in these “gentle” formulations.⁷ However, to avoid anchoring bias, more frequent causes of dermatitis should be included in the differential diagnosis. Textile ACD presents beneath clothing with accentuation at areas of closest contact with the skin, classically involving the axillary rim but sparing the vault. The most frequently implicated allergens in textile ACD are disperse dyes and less commonly textile resins.^33,34 Between 2017 and 2018, 2.3% of 4882 patients patch tested by the NACDG reacted positively to disperse dye mix.¹⁰ There is evidence to suggest that the actual prevalence of disperse dye allergy might be higher due to inadequacy of screening allergens on baseline patch test series.³⁵ Additional diagnoses that should be distinguished from presumed detergent contact dermatitis include atopic dermatitis and cutaneous T-cell lymphoma.

Final Interpretation

Although many patients and physicians consider laundry detergent to be a major cause of ACD, there is limited high-quality evidence to support this belief. Contact allergy to laundry detergent is probably much less common than is widely supposed. Although laundry detergents can contain common allergens such as fragrances and preservatives, evidence suggests that they are likely reduced to below clinically relevant levels during routine machine washing; however, we cannot assume that we are in the “free and clear,” as uncertainty remains about the impact of these low concentrationson individuals with strong contact allergy, and large studies of patch testing to modern detergents have yet to be carried out.

Laundry detergent, a cleaning agent ubiquitous in the modern household, often is suspected as a cause of allergic contact dermatitis (ACD). In one North American study, 10.7% of 738 patients undergoing patch testing believed that laundry detergent was a contributing factor, whereas their referring physicians had the same concern less often (in 2.3% of cases).¹Likewise, in a 1992 survey of western US households, more than 20% of 3841 respondents reported skin or health problems attributed to a textile and/or laundry product.² The suspicion of laundry detergent as a causative agent of ACD is perpetuated across popular wellness and beauty websites.^3,4 Does the evidence support this degree of suspicion? Or, similar to the well-meaning parent who misguidedly fixates on foods as the cause of their child’s atopic dermatitis and believes elimination diets are the solution,⁵ could a similar desire for control in the face of the unpredictability of eczema drive consumers and health care providers alike to blame laundry detergent—a familiar and modifiable cause?

We provide a summary of the evidence for the potential allergenicity of laundry detergent, including common allergens present in laundry detergent, the role of machine washing, and the differential diagnosis for laundry detergent–associated ACD.

Allergenic Ingredients in Laundry Detergent

Potential allergens present in laundry detergent include fragrances, preservatives, surfactants, emulsifiers, bleaches, brighteners, enzymes, and dyes.^6-8 In an analysis of allergens present in laundry detergents available in the United States, fragrances and preservatives were most common (eTable).^7,8 Contact allergy to fragrances occurs in approximately 3.5% of the general population⁹ and is detected in as many as 9.2% of patients referred for patch testing in North America.¹⁰ Preservatives commonly found in laundry detergent include isothiazolinones, such as methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI), MI alone, and benzisothiazolinone (BIT). Methylisothiazolinone has gained attention for causing an ACD epidemic beginning in the early 2000s and peaking in Europe between 2013 and 2014 and decreasing thereafter due to consumer personal care product regulatory changes enacted in the European Union.¹¹ In contrast, rates of MI allergy in North America have continued to increase (reaching as high as 15% of patch tested patients in 2017-2018) due to a lack of similar regulation.^10,12 More recently, the prevalence of positive patch tests to BIT has been rising, though it often is difficult to ascertain relevant sources of exposure, and some cases could represent cross-reactions to MCI/MI.^10,13

Other allergens that may be present in laundry detergent include surfactants and propylene glycol. Alkyl glucosides such as decyl glucoside and lauryl glucoside are considered gentle surfactants and often are included in products marketed as safe for sensitive skin,¹⁴ such as “free and gentle” detergents.⁸ However, they actually may pose an increased risk for sensitization in patients with atopic dermatitis.¹⁴ In addition to being allergenic, surfactants and emulsifiers are known irritants.^6,15 Although pathologically distinct, ACD and irritant contact dermatitis can be indistinguishable on clinical presentation.

How Commonly Does Laundry Detergent Cause ACD?

The mere presence of a contact allergen in laundry detergent does not necessarily imply that it is likely to cause ACD. To do so, the chemical in question must exceed the exposure thresholds for primary sensitization (ie, induction of contact allergy) and/or elicitation (ie, development of ACD in sensitized individuals). These depend on a complex interplay of product- and patient-specific factors, among them the concentration of the chemical in the detergent, the method of use, and the amount of detergent residue remaining on clothing after washing.

In the 1990s, the North American Contact Dermatitis Group (NACDG) attempted to determine the prevalence of ACD caused by laundry detergent.¹ Among 738 patients patch tested to aqueous dilutions of granular and liquid laundry detergents, only 5 (0.7%) had a possible allergic patch test reaction. It was unclear what the culprit allergens in the detergents may have been; only 1 of the patients also tested positive to fragrance. Two patients underwent further testing to additional detergent dilutions, and the results called into question whether their initial reactions had truly been allergic (positive) or were actually irritant (negative). The investigators concluded that the prevalence of laundry detergent–associated ACD in this large group of patients was at most 0.7%, and possibly lower.¹

Importantly, patch testing to laundry detergents should not be undertaken in routine clinical practice. Laundry detergents should never be tested “as is” (ie, undiluted) on the skin; they are inherently irritating and have a high likelihood of producing misleading false-positive reactions. Careful dilutions and testing of control subjects are necessary if patch testing with these products is to be appropriately conducted.

The extremely low prevalence of laundry detergent–associated ACD reported by the NACDG was determined prior to the start of the worldwide MI allergy epidemic, raising the possibility that laundry detergents containing isothiazolinones may be associated with ACD. There is no consensus about the minimum level at which isothiazolinones pose no risk to consumers,^16-19 but the US Expert Panel for Cosmetic Ingredient Safety declared that MI is “safe for use in rinse-off cosmetic products at concentrations up to 100 ppm and safe in leave-on cosmetic products when they are formulated to be nonsensitizing.”^18,19 Although ingredient lists do not always reveal when isothiazolinones are present, analyses of commercially available laundry detergents have shown MI concentrations ranging from undetectable to 65.7 ppm.^20-23

Published reports suggest that MCI/MI in laundry detergent can elicit ACD in sensitized individuals. In one case, a 7-year-old girl with chronic truncal dermatitis (atopic history unspecified) was patch tested, revealing a strongly positive reaction to MCI/MI.²⁴ Her laundry detergent was the only personal product found to contain MI. The dermatitis completely resolved after switching detergents and flared after wearing a jacket that had been washed in the implicated detergent, further supporting the relevance of the positive patch test. The investigators suspected initial sensitization to MI from wet wipes used earlier in childhood.²⁴ In another case involving occupational exposure, a 39-year-old nonatopic factory worker was responsible for directly adding MI to laundry detergent.²⁵ Although he wore disposable work gloves, he developed severe hand dermatitis, eczematous pretibial patches, and generalized pruritus. Patch testing revealed positive reactions to MCI/MI and MI, and he experienced improvement when reassigned to different work duties. It was hypothesized that the leg dermatitis and generalized pruritus may have been related to exposure to small concentrations of MI in work clothes washed with an MI-containing detergent.²⁵ Notably, this patient’s level of exposure was much greater than that encountered by individuals in day-to-day life outside of specialized occupational settings.

Regarding other isothiazolinones, a toxicologic study estimated that BIT in laundry detergent would be unlikely to induce sensitization, even at the maximal acceptable concentration, as recommended by preservative manufacturers, and accounting for undiluted detergent spilling directly onto the skin.²⁶Nonetheless, a single European center recently reported that almost half of the 38 patients with positive patch tests to BIT had a potentially relevant exposure attributed to household cleaning products, including laundry detergent.¹³ This emphasizes the need for further examination of sources of exposure to this increasingly common positive patch test allergen.

Does Machine Washing Impact Allergen Concentrations?

Two recent investigations have suggested that machine washing reduces concentrations of isothiazolinones to levels that are likely below clinical relevance. In the first study, 3 fabrics—cotton, polyester, cotton-polyester—were machine washed and line dried.²⁷ A standard detergent was used with MI added at different concentrations: less than 1 ppm, 100 ppm, and 1000 ppm. This process was either performed once or 10 times. Following laundering and line drying, MI was undetectable in all fabrics regardless of MI concentration or number of times washed (detection limit, 0.5 ppm).²⁷ In the second study, 4 fabrics—cotton, wool, polyester, linen—were washed with standard laundry detergent in 1 of 4 ways: handwashing (positive control), standard machine washing, standard machine washing with fabric softener, and standard machine washing with a double rinse.²⁸ After laundering and line drying, concentrations of MI, MCI, and BIT were low or undetectable regardless of fabric type or method of laundering. The highest levels detected were in handwashed garments at a maximum of 0.5 ppm of MI. The study authors postulated that chemical concentrations near these maximum residual levels may pose a risk for eliciting ACD in highly sensitized individuals. Therefore, handwashing can be considered a much higher risk activity for isothiazolinone ACD compared with machine washing.²⁸

It is intriguing that machine washing appears to reduce isothiazolinones to low concentrations that may have limited likelihood of causing ACD. Similar findings have been reported regarding fragrances. A quantitative risk assessment performed on 24 of 26 fragrance allergens regulated by the European Union determined that the amount of fragrance deposited on the skin from laundered garments would be less than the threshold for causing sensitization.²⁹ Although this risk assessment was unable to address the threshold of elicitation, another study conducted in Europe investigated whether fragrance residues present on fabric, such as those deposited from laundry detergent, are present at high enough concentrations to elicit ACD in previously sensitized individuals.³⁰ When 36 individuals were patch tested with increasing concentrations of a fragrance to which they were already sensitized, only 2 (5.6%) had a weakly positive reaction and then only to the highest concentration, which was estimated to be 20-fold higher than the level of skin exposure after normal laundering. No patient reacted at lower concentrations.³⁰

Although machine washing may decrease isothiazolinone and/or fragrance concentrations in laundry detergent to below clinically relevant levels, these findings should not necessarily be extrapolated to all chemicals in laundry detergent. Indeed, a prior study observed that after washing cotton cloths in a detergent solution for 10 minutes, detergent residue was present at concentrations ranging from 139 to 2820 ppm and required a subsequent 20 to 22 washes in water to become undetectable.³¹ Another study produced a mathematical model of the residual concentration of sodium dodecyl sulphate (SDS), a surfactant and known irritant, in laundered clothing.³² It was estimated that after machine washing, the residual concentration of SDS on clothes would be too low to cause irritation; however, as the clothes dry (ie, as moisture evaporates but solutes remain), the concentration of SDS on the fabric’s surface would increase to potentially irritating levels. The extensive drying that is possible with electric dryers may further enhance this solute-concentrating effect.

Differential Diagnosis of Laundry Detergent ACD

The propensity for laundry detergent to cause ACD is a question that is nowhere near settled, but the prevalence of allergy likely is far less common than is generally suspected. In our experience, many patients presenting for patch testing have already made the change to “free and clear” detergents without noticeable improvement in their dermatitis, which could possibly relate to the ongoing presence of contact allergens in these “gentle” formulations.⁷ However, to avoid anchoring bias, more frequent causes of dermatitis should be included in the differential diagnosis. Textile ACD presents beneath clothing with accentuation at areas of closest contact with the skin, classically involving the axillary rim but sparing the vault. The most frequently implicated allergens in textile ACD are disperse dyes and less commonly textile resins.^33,34 Between 2017 and 2018, 2.3% of 4882 patients patch tested by the NACDG reacted positively to disperse dye mix.¹⁰ There is evidence to suggest that the actual prevalence of disperse dye allergy might be higher due to inadequacy of screening allergens on baseline patch test series.³⁵ Additional diagnoses that should be distinguished from presumed detergent contact dermatitis include atopic dermatitis and cutaneous T-cell lymphoma.

Final Interpretation

Although many patients and physicians consider laundry detergent to be a major cause of ACD, there is limited high-quality evidence to support this belief. Contact allergy to laundry detergent is probably much less common than is widely supposed. Although laundry detergents can contain common allergens such as fragrances and preservatives, evidence suggests that they are likely reduced to below clinically relevant levels during routine machine washing; however, we cannot assume that we are in the “free and clear,” as uncertainty remains about the impact of these low concentrationson individuals with strong contact allergy, and large studies of patch testing to modern detergents have yet to be carried out.

Laundry detergent, a cleaning agent ubiquitous in the modern household, often is suspected as a cause of allergic contact dermatitis (ACD). In one North American study, 10.7% of 738 patients undergoing patch testing believed that laundry detergent was a contributing factor, whereas their referring physicians had the same concern less often (in 2.3% of cases).¹Likewise, in a 1992 survey of western US households, more than 20% of 3841 respondents reported skin or health problems attributed to a textile and/or laundry product.² The suspicion of laundry detergent as a causative agent of ACD is perpetuated across popular wellness and beauty websites.^3,4 Does the evidence support this degree of suspicion? Or, similar to the well-meaning parent who misguidedly fixates on foods as the cause of their child’s atopic dermatitis and believes elimination diets are the solution,⁵ could a similar desire for control in the face of the unpredictability of eczema drive consumers and health care providers alike to blame laundry detergent—a familiar and modifiable cause?

We provide a summary of the evidence for the potential allergenicity of laundry detergent, including common allergens present in laundry detergent, the role of machine washing, and the differential diagnosis for laundry detergent–associated ACD.

Allergenic Ingredients in Laundry Detergent

Potential allergens present in laundry detergent include fragrances, preservatives, surfactants, emulsifiers, bleaches, brighteners, enzymes, and dyes.^6-8 In an analysis of allergens present in laundry detergents available in the United States, fragrances and preservatives were most common (eTable).^7,8 Contact allergy to fragrances occurs in approximately 3.5% of the general population⁹ and is detected in as many as 9.2% of patients referred for patch testing in North America.¹⁰ Preservatives commonly found in laundry detergent include isothiazolinones, such as methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI), MI alone, and benzisothiazolinone (BIT). Methylisothiazolinone has gained attention for causing an ACD epidemic beginning in the early 2000s and peaking in Europe between 2013 and 2014 and decreasing thereafter due to consumer personal care product regulatory changes enacted in the European Union.¹¹ In contrast, rates of MI allergy in North America have continued to increase (reaching as high as 15% of patch tested patients in 2017-2018) due to a lack of similar regulation.^10,12 More recently, the prevalence of positive patch tests to BIT has been rising, though it often is difficult to ascertain relevant sources of exposure, and some cases could represent cross-reactions to MCI/MI.^10,13

Other allergens that may be present in laundry detergent include surfactants and propylene glycol. Alkyl glucosides such as decyl glucoside and lauryl glucoside are considered gentle surfactants and often are included in products marketed as safe for sensitive skin,¹⁴ such as “free and gentle” detergents.⁸ However, they actually may pose an increased risk for sensitization in patients with atopic dermatitis.¹⁴ In addition to being allergenic, surfactants and emulsifiers are known irritants.^6,15 Although pathologically distinct, ACD and irritant contact dermatitis can be indistinguishable on clinical presentation.

How Commonly Does Laundry Detergent Cause ACD?

The mere presence of a contact allergen in laundry detergent does not necessarily imply that it is likely to cause ACD. To do so, the chemical in question must exceed the exposure thresholds for primary sensitization (ie, induction of contact allergy) and/or elicitation (ie, development of ACD in sensitized individuals). These depend on a complex interplay of product- and patient-specific factors, among them the concentration of the chemical in the detergent, the method of use, and the amount of detergent residue remaining on clothing after washing.

In the 1990s, the North American Contact Dermatitis Group (NACDG) attempted to determine the prevalence of ACD caused by laundry detergent.¹ Among 738 patients patch tested to aqueous dilutions of granular and liquid laundry detergents, only 5 (0.7%) had a possible allergic patch test reaction. It was unclear what the culprit allergens in the detergents may have been; only 1 of the patients also tested positive to fragrance. Two patients underwent further testing to additional detergent dilutions, and the results called into question whether their initial reactions had truly been allergic (positive) or were actually irritant (negative). The investigators concluded that the prevalence of laundry detergent–associated ACD in this large group of patients was at most 0.7%, and possibly lower.¹

Importantly, patch testing to laundry detergents should not be undertaken in routine clinical practice. Laundry detergents should never be tested “as is” (ie, undiluted) on the skin; they are inherently irritating and have a high likelihood of producing misleading false-positive reactions. Careful dilutions and testing of control subjects are necessary if patch testing with these products is to be appropriately conducted.

The extremely low prevalence of laundry detergent–associated ACD reported by the NACDG was determined prior to the start of the worldwide MI allergy epidemic, raising the possibility that laundry detergents containing isothiazolinones may be associated with ACD. There is no consensus about the minimum level at which isothiazolinones pose no risk to consumers,^16-19 but the US Expert Panel for Cosmetic Ingredient Safety declared that MI is “safe for use in rinse-off cosmetic products at concentrations up to 100 ppm and safe in leave-on cosmetic products when they are formulated to be nonsensitizing.”^18,19 Although ingredient lists do not always reveal when isothiazolinones are present, analyses of commercially available laundry detergents have shown MI concentrations ranging from undetectable to 65.7 ppm.^20-23

Published reports suggest that MCI/MI in laundry detergent can elicit ACD in sensitized individuals. In one case, a 7-year-old girl with chronic truncal dermatitis (atopic history unspecified) was patch tested, revealing a strongly positive reaction to MCI/MI.²⁴ Her laundry detergent was the only personal product found to contain MI. The dermatitis completely resolved after switching detergents and flared after wearing a jacket that had been washed in the implicated detergent, further supporting the relevance of the positive patch test. The investigators suspected initial sensitization to MI from wet wipes used earlier in childhood.²⁴ In another case involving occupational exposure, a 39-year-old nonatopic factory worker was responsible for directly adding MI to laundry detergent.²⁵ Although he wore disposable work gloves, he developed severe hand dermatitis, eczematous pretibial patches, and generalized pruritus. Patch testing revealed positive reactions to MCI/MI and MI, and he experienced improvement when reassigned to different work duties. It was hypothesized that the leg dermatitis and generalized pruritus may have been related to exposure to small concentrations of MI in work clothes washed with an MI-containing detergent.²⁵ Notably, this patient’s level of exposure was much greater than that encountered by individuals in day-to-day life outside of specialized occupational settings.

Regarding other isothiazolinones, a toxicologic study estimated that BIT in laundry detergent would be unlikely to induce sensitization, even at the maximal acceptable concentration, as recommended by preservative manufacturers, and accounting for undiluted detergent spilling directly onto the skin.²⁶Nonetheless, a single European center recently reported that almost half of the 38 patients with positive patch tests to BIT had a potentially relevant exposure attributed to household cleaning products, including laundry detergent.¹³ This emphasizes the need for further examination of sources of exposure to this increasingly common positive patch test allergen.

Does Machine Washing Impact Allergen Concentrations?

Two recent investigations have suggested that machine washing reduces concentrations of isothiazolinones to levels that are likely below clinical relevance. In the first study, 3 fabrics—cotton, polyester, cotton-polyester—were machine washed and line dried.²⁷ A standard detergent was used with MI added at different concentrations: less than 1 ppm, 100 ppm, and 1000 ppm. This process was either performed once or 10 times. Following laundering and line drying, MI was undetectable in all fabrics regardless of MI concentration or number of times washed (detection limit, 0.5 ppm).²⁷ In the second study, 4 fabrics—cotton, wool, polyester, linen—were washed with standard laundry detergent in 1 of 4 ways: handwashing (positive control), standard machine washing, standard machine washing with fabric softener, and standard machine washing with a double rinse.²⁸ After laundering and line drying, concentrations of MI, MCI, and BIT were low or undetectable regardless of fabric type or method of laundering. The highest levels detected were in handwashed garments at a maximum of 0.5 ppm of MI. The study authors postulated that chemical concentrations near these maximum residual levels may pose a risk for eliciting ACD in highly sensitized individuals. Therefore, handwashing can be considered a much higher risk activity for isothiazolinone ACD compared with machine washing.²⁸

It is intriguing that machine washing appears to reduce isothiazolinones to low concentrations that may have limited likelihood of causing ACD. Similar findings have been reported regarding fragrances. A quantitative risk assessment performed on 24 of 26 fragrance allergens regulated by the European Union determined that the amount of fragrance deposited on the skin from laundered garments would be less than the threshold for causing sensitization.²⁹ Although this risk assessment was unable to address the threshold of elicitation, another study conducted in Europe investigated whether fragrance residues present on fabric, such as those deposited from laundry detergent, are present at high enough concentrations to elicit ACD in previously sensitized individuals.³⁰ When 36 individuals were patch tested with increasing concentrations of a fragrance to which they were already sensitized, only 2 (5.6%) had a weakly positive reaction and then only to the highest concentration, which was estimated to be 20-fold higher than the level of skin exposure after normal laundering. No patient reacted at lower concentrations.³⁰

Although machine washing may decrease isothiazolinone and/or fragrance concentrations in laundry detergent to below clinically relevant levels, these findings should not necessarily be extrapolated to all chemicals in laundry detergent. Indeed, a prior study observed that after washing cotton cloths in a detergent solution for 10 minutes, detergent residue was present at concentrations ranging from 139 to 2820 ppm and required a subsequent 20 to 22 washes in water to become undetectable.³¹ Another study produced a mathematical model of the residual concentration of sodium dodecyl sulphate (SDS), a surfactant and known irritant, in laundered clothing.³² It was estimated that after machine washing, the residual concentration of SDS on clothes would be too low to cause irritation; however, as the clothes dry (ie, as moisture evaporates but solutes remain), the concentration of SDS on the fabric’s surface would increase to potentially irritating levels. The extensive drying that is possible with electric dryers may further enhance this solute-concentrating effect.

Differential Diagnosis of Laundry Detergent ACD

The propensity for laundry detergent to cause ACD is a question that is nowhere near settled, but the prevalence of allergy likely is far less common than is generally suspected. In our experience, many patients presenting for patch testing have already made the change to “free and clear” detergents without noticeable improvement in their dermatitis, which could possibly relate to the ongoing presence of contact allergens in these “gentle” formulations.⁷ However, to avoid anchoring bias, more frequent causes of dermatitis should be included in the differential diagnosis. Textile ACD presents beneath clothing with accentuation at areas of closest contact with the skin, classically involving the axillary rim but sparing the vault. The most frequently implicated allergens in textile ACD are disperse dyes and less commonly textile resins.^33,34 Between 2017 and 2018, 2.3% of 4882 patients patch tested by the NACDG reacted positively to disperse dye mix.¹⁰ There is evidence to suggest that the actual prevalence of disperse dye allergy might be higher due to inadequacy of screening allergens on baseline patch test series.³⁵ Additional diagnoses that should be distinguished from presumed detergent contact dermatitis include atopic dermatitis and cutaneous T-cell lymphoma.

Final Interpretation

Although many patients and physicians consider laundry detergent to be a major cause of ACD, there is limited high-quality evidence to support this belief. Contact allergy to laundry detergent is probably much less common than is widely supposed. Although laundry detergents can contain common allergens such as fragrances and preservatives, evidence suggests that they are likely reduced to below clinically relevant levels during routine machine washing; however, we cannot assume that we are in the “free and clear,” as uncertainty remains about the impact of these low concentrationson individuals with strong contact allergy, and large studies of patch testing to modern detergents have yet to be carried out.

NEW ORLEANS – Among individuals who were surveyed at a health fair, most of whom were persons of color, 57% self-reported having sensitive skin.

Respondents also reported high rates of reactions to skin care products marketed for sensitive skin, and most said they had visited a dermatologist about their condition.

Those are among the key findings of a pilot study designed to assess the prevalence, symptom burden, and behaviors of self-identified persons of color with sensitive skin, which senior author Adam Friedman, MD, and colleagues defined as a subjective syndrome of cutaneous hyperreactivity to otherwise innocuous stimuli. “Improved understanding of sensitive skin is essential, and we encourage additional research into pathophysiology and creating a consensus definition for sensitive skin,” Dr. Friedman, professor and chair of dermatology at George Washington University, Washington, said in an interview in advance of the annual meeting of the American Academy of Dermatology, where the study was presented during an e-poster session. The findings were also reported online in JAAD International.

In May of 2022, Dr. Friedman, first author Erika McCormick, a 4th-year medical student at George Washington University, and colleagues invited individuals attending a community health fair in an undeserved area of Washington, to complete the Sensitive Scale-10 (SS-10) and to answer other questions after receiving a brief education about sensitive skin. Of the 58 respondents, 78% were female, and 86% self-identified as a person of color.

“Our study population predominantly self-identified as Black, which only represents one piece of those who would be characterized as persons of color,” Dr. Friedman said. “That said, improved representation of both our study population, and furthermore persons of color, in all aspects of dermatology research is crucial to at a minimum ensure generalizability of findings to the U.S. population, and research on sensitive skin is but one component of this.”

Nearly two-thirds of all respondents (63.8%) reported having an underlying skin condition, most commonly acne (21%), eczema (17%), and rosacea (6%). More than half (57%) reported sensitive skin, 27% of whom reported no other skin disease. Individuals with sensitive skin had higher mean SS-10 scores, compared with those with nonsensitive skin (14.61 vs. 4.32; P = .002) and burning was the main symptom among those with sensitive skin (56%), followed by itch (50%), redness (39%), dryness (39%) and pain (17%).

Compared with those who did not meet criteria for sensitive skin, those who did were more likely to report a personal history of allergy (56.25% vs. 8.33%; P = .0002) and were nearly seven times more likely to have seen a dermatologist about their concerns (odds ratio, 6.857; P = .0012).

In other findings limited to respondents with sensitive skin, 72% who reported reactions to general consumer skin care products also reported reacting to products marketed for sensitive skin, and 94% reported reactivity to at least one trigger, most commonly extreme temperatures (34%), stress (34%), sweat (33%), sun exposure (29%), and diet (28%). “We were particularly surprised by the high rates of reactivity to skin care products designed for and marketed to those suffering with sensitive skin,” Ms. McCormick told this news organization. “Importantly, there is currently no federal or legal standard regulating ingredients in products marketed for sensitive skin, and many products lack testing in sensitive skin specifically. Our data suggest an opportunity for improvement of sensitive skin care.”

She acknowledged certain limitations of the study, including its small sample size. “Reconducting this survey in a larger population will help validate our findings,” she said.

The research was supported by two independent research grants from Galderma: one supporting Ms. McCormick with a Sensitive Skin Research Fellowship and the other a Sensitive Skin Research Acceleration Fund. Dr. Friedman reported having no relevant disclosures.

NEW ORLEANS – Among individuals who were surveyed at a health fair, most of whom were persons of color, 57% self-reported having sensitive skin.

Respondents also reported high rates of reactions to skin care products marketed for sensitive skin, and most said they had visited a dermatologist about their condition.

Those are among the key findings of a pilot study designed to assess the prevalence, symptom burden, and behaviors of self-identified persons of color with sensitive skin, which senior author Adam Friedman, MD, and colleagues defined as a subjective syndrome of cutaneous hyperreactivity to otherwise innocuous stimuli. “Improved understanding of sensitive skin is essential, and we encourage additional research into pathophysiology and creating a consensus definition for sensitive skin,” Dr. Friedman, professor and chair of dermatology at George Washington University, Washington, said in an interview in advance of the annual meeting of the American Academy of Dermatology, where the study was presented during an e-poster session. The findings were also reported online in JAAD International.

In May of 2022, Dr. Friedman, first author Erika McCormick, a 4th-year medical student at George Washington University, and colleagues invited individuals attending a community health fair in an undeserved area of Washington, to complete the Sensitive Scale-10 (SS-10) and to answer other questions after receiving a brief education about sensitive skin. Of the 58 respondents, 78% were female, and 86% self-identified as a person of color.

“Our study population predominantly self-identified as Black, which only represents one piece of those who would be characterized as persons of color,” Dr. Friedman said. “That said, improved representation of both our study population, and furthermore persons of color, in all aspects of dermatology research is crucial to at a minimum ensure generalizability of findings to the U.S. population, and research on sensitive skin is but one component of this.”

Nearly two-thirds of all respondents (63.8%) reported having an underlying skin condition, most commonly acne (21%), eczema (17%), and rosacea (6%). More than half (57%) reported sensitive skin, 27% of whom reported no other skin disease. Individuals with sensitive skin had higher mean SS-10 scores, compared with those with nonsensitive skin (14.61 vs. 4.32; P = .002) and burning was the main symptom among those with sensitive skin (56%), followed by itch (50%), redness (39%), dryness (39%) and pain (17%).

Compared with those who did not meet criteria for sensitive skin, those who did were more likely to report a personal history of allergy (56.25% vs. 8.33%; P = .0002) and were nearly seven times more likely to have seen a dermatologist about their concerns (odds ratio, 6.857; P = .0012).

In other findings limited to respondents with sensitive skin, 72% who reported reactions to general consumer skin care products also reported reacting to products marketed for sensitive skin, and 94% reported reactivity to at least one trigger, most commonly extreme temperatures (34%), stress (34%), sweat (33%), sun exposure (29%), and diet (28%). “We were particularly surprised by the high rates of reactivity to skin care products designed for and marketed to those suffering with sensitive skin,” Ms. McCormick told this news organization. “Importantly, there is currently no federal or legal standard regulating ingredients in products marketed for sensitive skin, and many products lack testing in sensitive skin specifically. Our data suggest an opportunity for improvement of sensitive skin care.”

She acknowledged certain limitations of the study, including its small sample size. “Reconducting this survey in a larger population will help validate our findings,” she said.

The research was supported by two independent research grants from Galderma: one supporting Ms. McCormick with a Sensitive Skin Research Fellowship and the other a Sensitive Skin Research Acceleration Fund. Dr. Friedman reported having no relevant disclosures.

NEW ORLEANS – Among individuals who were surveyed at a health fair, most of whom were persons of color, 57% self-reported having sensitive skin.

Respondents also reported high rates of reactions to skin care products marketed for sensitive skin, and most said they had visited a dermatologist about their condition.

Those are among the key findings of a pilot study designed to assess the prevalence, symptom burden, and behaviors of self-identified persons of color with sensitive skin, which senior author Adam Friedman, MD, and colleagues defined as a subjective syndrome of cutaneous hyperreactivity to otherwise innocuous stimuli. “Improved understanding of sensitive skin is essential, and we encourage additional research into pathophysiology and creating a consensus definition for sensitive skin,” Dr. Friedman, professor and chair of dermatology at George Washington University, Washington, said in an interview in advance of the annual meeting of the American Academy of Dermatology, where the study was presented during an e-poster session. The findings were also reported online in JAAD International.

In May of 2022, Dr. Friedman, first author Erika McCormick, a 4th-year medical student at George Washington University, and colleagues invited individuals attending a community health fair in an undeserved area of Washington, to complete the Sensitive Scale-10 (SS-10) and to answer other questions after receiving a brief education about sensitive skin. Of the 58 respondents, 78% were female, and 86% self-identified as a person of color.

“Our study population predominantly self-identified as Black, which only represents one piece of those who would be characterized as persons of color,” Dr. Friedman said. “That said, improved representation of both our study population, and furthermore persons of color, in all aspects of dermatology research is crucial to at a minimum ensure generalizability of findings to the U.S. population, and research on sensitive skin is but one component of this.”

Nearly two-thirds of all respondents (63.8%) reported having an underlying skin condition, most commonly acne (21%), eczema (17%), and rosacea (6%). More than half (57%) reported sensitive skin, 27% of whom reported no other skin disease. Individuals with sensitive skin had higher mean SS-10 scores, compared with those with nonsensitive skin (14.61 vs. 4.32; P = .002) and burning was the main symptom among those with sensitive skin (56%), followed by itch (50%), redness (39%), dryness (39%) and pain (17%).

Compared with those who did not meet criteria for sensitive skin, those who did were more likely to report a personal history of allergy (56.25% vs. 8.33%; P = .0002) and were nearly seven times more likely to have seen a dermatologist about their concerns (odds ratio, 6.857; P = .0012).

In other findings limited to respondents with sensitive skin, 72% who reported reactions to general consumer skin care products also reported reacting to products marketed for sensitive skin, and 94% reported reactivity to at least one trigger, most commonly extreme temperatures (34%), stress (34%), sweat (33%), sun exposure (29%), and diet (28%). “We were particularly surprised by the high rates of reactivity to skin care products designed for and marketed to those suffering with sensitive skin,” Ms. McCormick told this news organization. “Importantly, there is currently no federal or legal standard regulating ingredients in products marketed for sensitive skin, and many products lack testing in sensitive skin specifically. Our data suggest an opportunity for improvement of sensitive skin care.”

She acknowledged certain limitations of the study, including its small sample size. “Reconducting this survey in a larger population will help validate our findings,” she said.

The research was supported by two independent research grants from Galderma: one supporting Ms. McCormick with a Sensitive Skin Research Fellowship and the other a Sensitive Skin Research Acceleration Fund. Dr. Friedman reported having no relevant disclosures.

The Diagnosis: Allergic Contact Dermatitis

This patient’s history and physical examination were most consistent with a diagnosis of allergic contact dermatitis, likely from an additive or diluent solution within the tattoo ink. Her history of a similar transient reaction following tattooing 2 weeks prior lent credence to an allergic etiology. She was treated with triamcinolone cream 0.1% as well as mupirocin ointment 2% for use as both an emollient and for precautionary antimicrobial coverage. The rash resolved within 2 days, and she reported no recurrence at a 6-month follow-up. The cosmesis of her tattoo was preserved.

Acute cellulitis may follow tattooing, but the absence of warmth, pain, or purulence on physical examination made this diagnosis less likely in this patient. Sarcoidosis or other granulomatous reactions may present as papules or nodules arising within a tattoo but would be unlikely to occur the next day. Nontuberculous mycobacterial infection likewise tends to present subacutely or chronically rather than immediately following tattoo application.

Tattooing has existed for millennia and is becoming increasingly popular.^1,2 The tattooing process entails introduction of insoluble pigment compounds into the dermis to create a permanent design on the skin, which most often is accomplished via needling. As a result, tattooed skin is susceptible to both acute and chronic complications. Acute complications prominently include allergic hypersensitivity reactions and pyogenic bacterial infections. Chronic granulomatous, inflammatory, or infectious complications also can occur.

Allergic eczematous reactions to tattooing are well documented in the literature and are thought to originate from sensitization to pigment molecules themselves or alternatively to ink diluent compounds.³ Although reactions to ink diluent chemicals typically are self-resolving, allergic reactions to pigment can persist beyond the acute phase, as these insoluble compounds intentionally remain embedded in the dermis. The mechanism of action may involve haptenization of pigment molecules that then induces allergic hypersensitivity.^3,4 Black pigment typically is derived from carbon black (ie, amorphous combustion byproducts such as soot). Colored inks historically consisted of inorganic heavy metal–containing salts prior to the modern introduction of synthetic azo and polycyclic dyes. These newer colored pigments appear to be less allergenic than their metallic predecessors; however, epidemiologic studies have suggested that allergic reactions still occur more commonly in colored tattoos than black tattoos.¹ Overall, these reactions may occur in as many as one-third of individuals who receive tattoos.^2,4

As with any process that disrupts skin integrity, tattooing carries a risk for transmitting various infectious pathogens. Microbes may originate from adjacent skin, contaminated needles, ink bottles, or nonsterile ink diluents. Although tattoo parlors and artists may undergo licensing to demonstrate adherence to hygienic standards, regulations vary between states and do not include testing of ink or ink additives to ensure sterility.^4,5 Staphylococci and streptococci commonly are implicated in acute pyogenic skin infections following tattooing.^5,6 Nontuberculous mycobacteria increasingly are being recognized as causative organisms for granulomatous lesions developing subacutely or even months after receiving a new tattoo.^5,7 Local and systemic viral infections also may be transmitted during tattooing; cases of tattoo-transmitted viral warts, molluscum contagiosum, and hepatitis B and C viruses all have been observed.^5,6,8 Herpes simplex virus transmission (colloquially termed herpes compunctorum) and HIV transmission through tattooing also are hypothesized to be possible, though there is a paucity of known cases for each.^8,9

Chronic inflammatory, granulomatous, or neoplastic lesions may arise within tattooed skin months or years after tattooing. Foreign body granulomas, sarcoidosis, pseudolymphoma, pseudoepitheliomatous hyperplasia, and keratoacanthoma are some representative entities.^3,5 Cases of cancerous lesions in tattooed skin have been documented, but their incidence appears similar to nontattooed skin.³ These broad categories of lesions are clinically diverse but may be difficult to definitively diagnose on examination alone; therefore, a biopsy should be strongly considered for any subacute to chronic skin lesions within a tattoo. Patients may be hesitant to disrupt the cosmesis of a tattoo but should be counseled on the attendant risks and benefits to make an informed decision regarding biopsy.

The Diagnosis: Allergic Contact Dermatitis

This patient’s history and physical examination were most consistent with a diagnosis of allergic contact dermatitis, likely from an additive or diluent solution within the tattoo ink. Her history of a similar transient reaction following tattooing 2 weeks prior lent credence to an allergic etiology. She was treated with triamcinolone cream 0.1% as well as mupirocin ointment 2% for use as both an emollient and for precautionary antimicrobial coverage. The rash resolved within 2 days, and she reported no recurrence at a 6-month follow-up. The cosmesis of her tattoo was preserved.

Acute cellulitis may follow tattooing, but the absence of warmth, pain, or purulence on physical examination made this diagnosis less likely in this patient. Sarcoidosis or other granulomatous reactions may present as papules or nodules arising within a tattoo but would be unlikely to occur the next day. Nontuberculous mycobacterial infection likewise tends to present subacutely or chronically rather than immediately following tattoo application.

Tattooing has existed for millennia and is becoming increasingly popular.^1,2 The tattooing process entails introduction of insoluble pigment compounds into the dermis to create a permanent design on the skin, which most often is accomplished via needling. As a result, tattooed skin is susceptible to both acute and chronic complications. Acute complications prominently include allergic hypersensitivity reactions and pyogenic bacterial infections. Chronic granulomatous, inflammatory, or infectious complications also can occur.

Allergic eczematous reactions to tattooing are well documented in the literature and are thought to originate from sensitization to pigment molecules themselves or alternatively to ink diluent compounds.³ Although reactions to ink diluent chemicals typically are self-resolving, allergic reactions to pigment can persist beyond the acute phase, as these insoluble compounds intentionally remain embedded in the dermis. The mechanism of action may involve haptenization of pigment molecules that then induces allergic hypersensitivity.^3,4 Black pigment typically is derived from carbon black (ie, amorphous combustion byproducts such as soot). Colored inks historically consisted of inorganic heavy metal–containing salts prior to the modern introduction of synthetic azo and polycyclic dyes. These newer colored pigments appear to be less allergenic than their metallic predecessors; however, epidemiologic studies have suggested that allergic reactions still occur more commonly in colored tattoos than black tattoos.¹ Overall, these reactions may occur in as many as one-third of individuals who receive tattoos.^2,4

As with any process that disrupts skin integrity, tattooing carries a risk for transmitting various infectious pathogens. Microbes may originate from adjacent skin, contaminated needles, ink bottles, or nonsterile ink diluents. Although tattoo parlors and artists may undergo licensing to demonstrate adherence to hygienic standards, regulations vary between states and do not include testing of ink or ink additives to ensure sterility.^4,5 Staphylococci and streptococci commonly are implicated in acute pyogenic skin infections following tattooing.^5,6 Nontuberculous mycobacteria increasingly are being recognized as causative organisms for granulomatous lesions developing subacutely or even months after receiving a new tattoo.^5,7 Local and systemic viral infections also may be transmitted during tattooing; cases of tattoo-transmitted viral warts, molluscum contagiosum, and hepatitis B and C viruses all have been observed.^5,6,8 Herpes simplex virus transmission (colloquially termed herpes compunctorum) and HIV transmission through tattooing also are hypothesized to be possible, though there is a paucity of known cases for each.^8,9

Chronic inflammatory, granulomatous, or neoplastic lesions may arise within tattooed skin months or years after tattooing. Foreign body granulomas, sarcoidosis, pseudolymphoma, pseudoepitheliomatous hyperplasia, and keratoacanthoma are some representative entities.^3,5 Cases of cancerous lesions in tattooed skin have been documented, but their incidence appears similar to nontattooed skin.³ These broad categories of lesions are clinically diverse but may be difficult to definitively diagnose on examination alone; therefore, a biopsy should be strongly considered for any subacute to chronic skin lesions within a tattoo. Patients may be hesitant to disrupt the cosmesis of a tattoo but should be counseled on the attendant risks and benefits to make an informed decision regarding biopsy.

The Diagnosis: Allergic Contact Dermatitis

This patient’s history and physical examination were most consistent with a diagnosis of allergic contact dermatitis, likely from an additive or diluent solution within the tattoo ink. Her history of a similar transient reaction following tattooing 2 weeks prior lent credence to an allergic etiology. She was treated with triamcinolone cream 0.1% as well as mupirocin ointment 2% for use as both an emollient and for precautionary antimicrobial coverage. The rash resolved within 2 days, and she reported no recurrence at a 6-month follow-up. The cosmesis of her tattoo was preserved.

Acute cellulitis may follow tattooing, but the absence of warmth, pain, or purulence on physical examination made this diagnosis less likely in this patient. Sarcoidosis or other granulomatous reactions may present as papules or nodules arising within a tattoo but would be unlikely to occur the next day. Nontuberculous mycobacterial infection likewise tends to present subacutely or chronically rather than immediately following tattoo application.

Tattooing has existed for millennia and is becoming increasingly popular.^1,2 The tattooing process entails introduction of insoluble pigment compounds into the dermis to create a permanent design on the skin, which most often is accomplished via needling. As a result, tattooed skin is susceptible to both acute and chronic complications. Acute complications prominently include allergic hypersensitivity reactions and pyogenic bacterial infections. Chronic granulomatous, inflammatory, or infectious complications also can occur.

Allergic eczematous reactions to tattooing are well documented in the literature and are thought to originate from sensitization to pigment molecules themselves or alternatively to ink diluent compounds.³ Although reactions to ink diluent chemicals typically are self-resolving, allergic reactions to pigment can persist beyond the acute phase, as these insoluble compounds intentionally remain embedded in the dermis. The mechanism of action may involve haptenization of pigment molecules that then induces allergic hypersensitivity.^3,4 Black pigment typically is derived from carbon black (ie, amorphous combustion byproducts such as soot). Colored inks historically consisted of inorganic heavy metal–containing salts prior to the modern introduction of synthetic azo and polycyclic dyes. These newer colored pigments appear to be less allergenic than their metallic predecessors; however, epidemiologic studies have suggested that allergic reactions still occur more commonly in colored tattoos than black tattoos.¹ Overall, these reactions may occur in as many as one-third of individuals who receive tattoos.^2,4

As with any process that disrupts skin integrity, tattooing carries a risk for transmitting various infectious pathogens. Microbes may originate from adjacent skin, contaminated needles, ink bottles, or nonsterile ink diluents. Although tattoo parlors and artists may undergo licensing to demonstrate adherence to hygienic standards, regulations vary between states and do not include testing of ink or ink additives to ensure sterility.^4,5 Staphylococci and streptococci commonly are implicated in acute pyogenic skin infections following tattooing.^5,6 Nontuberculous mycobacteria increasingly are being recognized as causative organisms for granulomatous lesions developing subacutely or even months after receiving a new tattoo.^5,7 Local and systemic viral infections also may be transmitted during tattooing; cases of tattoo-transmitted viral warts, molluscum contagiosum, and hepatitis B and C viruses all have been observed.^5,6,8 Herpes simplex virus transmission (colloquially termed herpes compunctorum) and HIV transmission through tattooing also are hypothesized to be possible, though there is a paucity of known cases for each.^8,9

Chronic inflammatory, granulomatous, or neoplastic lesions may arise within tattooed skin months or years after tattooing. Foreign body granulomas, sarcoidosis, pseudolymphoma, pseudoepitheliomatous hyperplasia, and keratoacanthoma are some representative entities.^3,5 Cases of cancerous lesions in tattooed skin have been documented, but their incidence appears similar to nontattooed skin.³ These broad categories of lesions are clinically diverse but may be difficult to definitively diagnose on examination alone; therefore, a biopsy should be strongly considered for any subacute to chronic skin lesions within a tattoo. Patients may be hesitant to disrupt the cosmesis of a tattoo but should be counseled on the attendant risks and benefits to make an informed decision regarding biopsy.

Lanolin, known mainly for its emollient properties, has been named by the American Contact Dermatitis Society as the Contact Allergen of the Year for 2023.

Lanolin is a complex and varying mixture of high molecular weight esters, aliphatic alcohols, sterols, fatty acids, and hydrocarbons, but the allergic components are mainly the free lanolin alcohols, especially alkanediols, said Donald V. Belsito, MD, professor of dermatology, Columbia University, New York, who announced the Allergen of the Year at the society’s annual meeting.

Criteria for selection can include a known allergen with a new twist or increasing frequency or a newly reported allergen with mini-epidemics that may have been missed for years, Dr. Belsito said.

“The prevalence and severity of allergy to ‘lanolin’ have been hotly debated” since a potential case was first reported in the 1920s, wrote Dr. Belsito and Blair A. Jenkins, MD, PhD, a dermatology resident at New York–Presbyterian Hospital, Columbia Campus, in a review published in Dermatitis.

“ ‘Lanolin’ is indeed a paradox allergen,” wrote Dr. Jenkins and Dr. Belsito. “The most appropriate patch test preparation(s) for detecting allergy remain disputed. Detection of lanolin-induced contact dermatitis in diseased skin by patch testing on normal skin may lead to false negative results.”

And those who test positive for a lanolin allergy on diseased skin may be able to use lanolin products on normal skin, they wrote.

“From my perspective, this was a timely year to think about lanolin, as there is significant ongoing controversy about whether it is allergenic,” Dr. Jenkins said in an interview. “Numerous companies market lanolin-containing topicals as safe and effective emollients,” she said.
 

Medical grade and highly purified anhydrous lanolin, which contain less than 2.5% and less than 1.5% of free alcohols, respectively, can still elicit or induce a contact allergy, Dr. Belsito said in his presentation. Hydrogenated lanolin has shown more allergenicity than lanolin alcohol, while lanolin wax, lanolin acid, and lanolin esters possess lower allergenicity than lanolin alcohol, he said.

Notably, modern wool textiles do not contain lanolin, and lanolin-allergic patients need not avoid wool, Dr. Belsito added.

Amerchol L-101, a common trade name on products containing lanolin, contains 10% wool wax alcohols obtained from the hydrolysis of wool fat dissolved in mineral oil at a 1:1 ratio, said Dr. Belsito. He recommended testing lanolin alcohols (in 30% petrolatum) and Amerchol L-101 (in 50% petrolatum) simultaneously with or without other lanolin derivatives and/or the patient’s products in cases of possible allergy, he said.
 

Consider high-risk groups

Current evidence suggests that the prevalence of contact allergy in the western European population is 0.4%, wrote Dr. Jenkins and Dr. Belsito.

Although the frequency of lanolin allergy is relatively low, certain conditions convey greater risk, such as stasis dermatitis, leg ulcers, perianal/genital dermatitis, and atopic dermatitis, they wrote. Older adults and children are at increased risk because they are more likely to have these conditions. Demographic data also suggest that lanolin allergy is more common in non-Hispanic Whites than in non-Hispanic Blacks, they wrote.

Looking ahead, “I think further exploration of allergy across different skin types and ethnicities is warranted,” Dr. Jenkins said. “Further investigation of ideal [lanolin] allergens for patch testing is also needed.”

Dr. Jenkins and Dr. Belsito said they had no relevant financial conflicts to disclose.

Lanolin, known mainly for its emollient properties, has been named by the American Contact Dermatitis Society as the Contact Allergen of the Year for 2023.

Lanolin is a complex and varying mixture of high molecular weight esters, aliphatic alcohols, sterols, fatty acids, and hydrocarbons, but the allergic components are mainly the free lanolin alcohols, especially alkanediols, said Donald V. Belsito, MD, professor of dermatology, Columbia University, New York, who announced the Allergen of the Year at the society’s annual meeting.

Criteria for selection can include a known allergen with a new twist or increasing frequency or a newly reported allergen with mini-epidemics that may have been missed for years, Dr. Belsito said.

“The prevalence and severity of allergy to ‘lanolin’ have been hotly debated” since a potential case was first reported in the 1920s, wrote Dr. Belsito and Blair A. Jenkins, MD, PhD, a dermatology resident at New York–Presbyterian Hospital, Columbia Campus, in a review published in Dermatitis.

“ ‘Lanolin’ is indeed a paradox allergen,” wrote Dr. Jenkins and Dr. Belsito. “The most appropriate patch test preparation(s) for detecting allergy remain disputed. Detection of lanolin-induced contact dermatitis in diseased skin by patch testing on normal skin may lead to false negative results.”

And those who test positive for a lanolin allergy on diseased skin may be able to use lanolin products on normal skin, they wrote.

“From my perspective, this was a timely year to think about lanolin, as there is significant ongoing controversy about whether it is allergenic,” Dr. Jenkins said in an interview. “Numerous companies market lanolin-containing topicals as safe and effective emollients,” she said.
 

Medical grade and highly purified anhydrous lanolin, which contain less than 2.5% and less than 1.5% of free alcohols, respectively, can still elicit or induce a contact allergy, Dr. Belsito said in his presentation. Hydrogenated lanolin has shown more allergenicity than lanolin alcohol, while lanolin wax, lanolin acid, and lanolin esters possess lower allergenicity than lanolin alcohol, he said.

Notably, modern wool textiles do not contain lanolin, and lanolin-allergic patients need not avoid wool, Dr. Belsito added.

Amerchol L-101, a common trade name on products containing lanolin, contains 10% wool wax alcohols obtained from the hydrolysis of wool fat dissolved in mineral oil at a 1:1 ratio, said Dr. Belsito. He recommended testing lanolin alcohols (in 30% petrolatum) and Amerchol L-101 (in 50% petrolatum) simultaneously with or without other lanolin derivatives and/or the patient’s products in cases of possible allergy, he said.
 

Consider high-risk groups

Current evidence suggests that the prevalence of contact allergy in the western European population is 0.4%, wrote Dr. Jenkins and Dr. Belsito.

Although the frequency of lanolin allergy is relatively low, certain conditions convey greater risk, such as stasis dermatitis, leg ulcers, perianal/genital dermatitis, and atopic dermatitis, they wrote. Older adults and children are at increased risk because they are more likely to have these conditions. Demographic data also suggest that lanolin allergy is more common in non-Hispanic Whites than in non-Hispanic Blacks, they wrote.

Looking ahead, “I think further exploration of allergy across different skin types and ethnicities is warranted,” Dr. Jenkins said. “Further investigation of ideal [lanolin] allergens for patch testing is also needed.”

Dr. Jenkins and Dr. Belsito said they had no relevant financial conflicts to disclose.

Lanolin, known mainly for its emollient properties, has been named by the American Contact Dermatitis Society as the Contact Allergen of the Year for 2023.

Lanolin is a complex and varying mixture of high molecular weight esters, aliphatic alcohols, sterols, fatty acids, and hydrocarbons, but the allergic components are mainly the free lanolin alcohols, especially alkanediols, said Donald V. Belsito, MD, professor of dermatology, Columbia University, New York, who announced the Allergen of the Year at the society’s annual meeting.

Criteria for selection can include a known allergen with a new twist or increasing frequency or a newly reported allergen with mini-epidemics that may have been missed for years, Dr. Belsito said.

“The prevalence and severity of allergy to ‘lanolin’ have been hotly debated” since a potential case was first reported in the 1920s, wrote Dr. Belsito and Blair A. Jenkins, MD, PhD, a dermatology resident at New York–Presbyterian Hospital, Columbia Campus, in a review published in Dermatitis.

“ ‘Lanolin’ is indeed a paradox allergen,” wrote Dr. Jenkins and Dr. Belsito. “The most appropriate patch test preparation(s) for detecting allergy remain disputed. Detection of lanolin-induced contact dermatitis in diseased skin by patch testing on normal skin may lead to false negative results.”

And those who test positive for a lanolin allergy on diseased skin may be able to use lanolin products on normal skin, they wrote.

“From my perspective, this was a timely year to think about lanolin, as there is significant ongoing controversy about whether it is allergenic,” Dr. Jenkins said in an interview. “Numerous companies market lanolin-containing topicals as safe and effective emollients,” she said.
 

Medical grade and highly purified anhydrous lanolin, which contain less than 2.5% and less than 1.5% of free alcohols, respectively, can still elicit or induce a contact allergy, Dr. Belsito said in his presentation. Hydrogenated lanolin has shown more allergenicity than lanolin alcohol, while lanolin wax, lanolin acid, and lanolin esters possess lower allergenicity than lanolin alcohol, he said.

Notably, modern wool textiles do not contain lanolin, and lanolin-allergic patients need not avoid wool, Dr. Belsito added.

Amerchol L-101, a common trade name on products containing lanolin, contains 10% wool wax alcohols obtained from the hydrolysis of wool fat dissolved in mineral oil at a 1:1 ratio, said Dr. Belsito. He recommended testing lanolin alcohols (in 30% petrolatum) and Amerchol L-101 (in 50% petrolatum) simultaneously with or without other lanolin derivatives and/or the patient’s products in cases of possible allergy, he said.
 

Consider high-risk groups

Current evidence suggests that the prevalence of contact allergy in the western European population is 0.4%, wrote Dr. Jenkins and Dr. Belsito.

Although the frequency of lanolin allergy is relatively low, certain conditions convey greater risk, such as stasis dermatitis, leg ulcers, perianal/genital dermatitis, and atopic dermatitis, they wrote. Older adults and children are at increased risk because they are more likely to have these conditions. Demographic data also suggest that lanolin allergy is more common in non-Hispanic Whites than in non-Hispanic Blacks, they wrote.

Looking ahead, “I think further exploration of allergy across different skin types and ethnicities is warranted,” Dr. Jenkins said. “Further investigation of ideal [lanolin] allergens for patch testing is also needed.”

Dr. Jenkins and Dr. Belsito said they had no relevant financial conflicts to disclose.