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It may not seem intuitive, but to understand some of the new skin care claims, you need to know a bit about the gut microbiome and its role in skin health. The The gut and skin play a balancing act between beneficial, neutral, and harmful flora that are interrelated with the innate and adaptive immune systems.1 The skin and gut seem to be intertwined and express several comorbidities.2 In this column, the focus is on the cutaneous microbiome’s role in skin health. To understand the cosmeceutical claims about pre- and probiotics, you first need to familiarize yourself with skin microbiome science. The skin-gut nexus will be discussed in next month’s column, which will address the role of the skin microbiome in skin diseases.
Why is the microbiome such a hot topic?
Genetic sequencing has spurred advances in the study of the microbiome and has provided intriguing clues that the gut and skin microbiome have influences on each other. Sequencing assays that focus on bacterial 16S ribosomal RNA genes have been used by investigators to distinguish and describe the wide variety of resident and transient microorganisms on the skin and elucidate their roles in skin health and disease.1 Genomic sequencing has identified species in the skin and gut that were not found previously by cultivating microbial isolates.3,4 Advances in technologies such as whole-genome shotgun sequencing, metagenomics, and functional metabolomics will further contribute to our understanding of the effects of the skin microbiome on skin health and skin type. Of course, many supplement and cosmeceutical companies have jumped on this bandwagon prematurely and claim that their products increase “good bacteria while diminishing bad bacteria.” While there are interesting data that have emerged, we still cannot say which bacteria are “good” and ‘bad” as far as the skin is concerned – with a few exceptions that we have known all along. For example, Cutibacterium acnes and Staphylococcus aureus still remain in the undesirable category. (P. acnes has been renamed and now is officially referred to as C. acnes.) While it is premature to recommend probiotic– or prebiotic–containing cosmeceuticals, your patients will ask you about them. New studies about rosacea and the microbiome have generated a lot of patient questions in my practice, so I am writing several blogs about how to answer patient questions, which can be found at STSFranchise.com/blog. I’m also educating consumers on Facebook and Instagram @skintypesolutions so that they will not be taken advantage of by the too early “pseudoscience.” So now that you have heard that it is too early to recommend pre- and probiotic skin care to target skin issues, let’s look at the science that does exist.
Terminology
- Microbiome: Microbes that live in a particular environment or biome.
- Microbiota: The collection of living microbes that live in or on an environment. This term includes the microorganisms only and not the characteristics of their environment.
- Prebiotics: A nondigestible food ingredient that promotes the growth of microorganisms in the intestines. These can promote the growth of beneficial or harmful microorganisms. Think of them as a type of “fertilizer” for the microbiome.
- Probiotics: Living microorganisms that can provide beneficial qualities when used orally or topically. What probiotics are not? Microbes naturally found in your body and on your skin; microbes that are no longer alive; fermented foods that contain an unknown amount of bacteria.
Skin surface area
Richard Gallo, MD, a dermatologist from the University of California, San Diego, who is a leader in the microbiome field of study, says that estimates of the cutaneous microbiome’s impact on human health via skin have failed to acknowledge the inner follicular surface, thus drastically undervaluing the potential of the cutaneous microbiome to influence systemic health.5 He suggests that the surface area of skin has been miscalculated as measuring 2 m2 because it is considered a flat surface. This ignores the plethora of hair follicles and sweat ducts that significantly broaden the epithelial surface to measure closer to 25 m2 and underscores that the expansive skin microbiome is much larger than previously recognized.5 Taking the hair follicle surface area into account, the skin has vast space to harbor various organisms and microbiome environments. What our patients use on their skin certainly influences these environments. The key is trying to figure out how to manipulate the microbiome to our patient’s advantage.
Microbes have environmental preferences
Different microbial species thrive on particular regions of the diverse topography of the expansive surface area and choose their preferred environments from among sebaceous or nonsebaceous, hairy or smooth, moist or dry, and creased or noncreased areas.6,7 Other host factors that affect which microorganisms colonize the skin include hair follicle thickness, age, sex, diet (especially high fat and sugar intake), climate, occupation, and personal hygiene.7-10 Gene sequencing has revealed that these variations are partially because of factors such as ultraviolet exposure, pH, and temperature.4,6,11 For example, C. acnes has been found to be more prevalent in highly sebaceous sites on the head and upper torso.4 In general, Propionibacteriaceae (Cutibacterium) prefer sebaceous areas, whereas Corynebacteriaceae and Staphylococcaceae prevail in moist regions, such as the navel or axilla. Dry areas host the widest diversity of microbes, including Corynebacterium, Staphylococcus, and Streptococcus species.1,7,12
Impact of sebum and skin hydration on microbiome
In 2016, Mukherjee et al. measured sebum and hydration from the forehead and cheeks of 30 healthy female volunteers in a study that tested the hypothesis that differences in sebum and hydration levels in specific facial areas account for interindividual variation in facial skin microbiome. They found that the most significant predictor of microbiome composition was cheek sebum level, followed by forehead hydration level, while cheek hydration and forehead sebum levels were not predictive. The prevalence of Actinobacteria/Propionibacterium rose, while microbiome diversity diminished with an increase in cheek sebum, with such trends reversed in relation to forehead hydration. The investigators concluded that site-specific sebum and water levels impact the nature and diversity of the facial skin microbiome.13
Lability of the cutaneous microbiome
The skin microbiome changes during various times of life. For example, in puberty, more lipophilic species such as Propionibacteriaceae and Cornebacteriaceae predominate, while prior to puberty there is a preponderance of Firmicutes, Bacteroidetes, and Proteobacteria.4,14 However, in the absence of lifestyle changes, cutaneous microbial communities have been found through longitudinal studies to be relatively stable over a 2-year period.6 A person’s skin microbiome is subject to influence from an adjacent skin microbiome, such as between cohabiting couples or the influence of breastfeeding mothers.15 It is never too early to consider the role of the microbiome in health and disease. For example, infant microbiomes play a role in eczema and the atopic march.16 For this reason, those of us who treat children need to be familiar with studies that have demonstrate how the cutaneous microbiome is affected by childbirth delivery method, breastfeeding, the mother’s diet antibiotic use during pregnancy and breastfeeding.4,17
Microbiome effects on skin function
The skin barrier, a bilayer lipid-laden membrane that surrounds keratinocytes and prevents transepidermal water loss, is affected by resident microbial communities and has been shown by research to be influenced by the volume and diversity of such microbes.18 Organisms on the skin’s surface play an important role in communicating with and educating the cutaneous arm of the immune system.19 In 2017, Maguire and Maguire reviewed recent studies of the gut and skin microbiomes and suggested that Nitrobacter, Lactobacillus, and Bifidobacterium can improve skin health and could be useful bacterial adjuvants in a probiotic and prebiotic strategy in homeostatic renormalization when skin health is compromised.20Nitrobacter has displayed antifungal activity against dermatophytes and Staphylococcus; Lactobacillus has exhibited anti-inflammatory effects and was shown to improve adult acne in a small study; Bifidobacterium combined with Lactobacillus lowered the incidence of atopic eczema in early childhood; and Bifidobacterium and the prebiotic galacto-oligosaccharide prevented hydration level losses in the stratum corneum among other beneficial effects in a double-blind, placebo-controlled, randomized trial.20
Microbiome diversity is key
Microbes interact, collaborate, and oppose one another while exerting influence and being affected by the host. Effective communication among the innate and adaptive parts of the immune system, epithelial cells, and cutaneous microbiota is essential for optimal functioning of the skin.6,7 Studies on subjects with atopic dermatitis showed a strong association between decreased diversity and increased disease severity. This suggests that a diverse microbiome is associated with skin health.21 For this reason, use of pre- and probiotics for skin issues is discouraged at this time. If we replace the normal diverse flora with one organism, we do not yet know the consequences. It is much more likely that successful treatments in the future will contain a diverse group of organisms.
Cosmeceutical effects on the skin microbiome
Cleansing and use of emollients certainly affect the skin biome, but we do not yet know to what extent. A study that looked at the effects of emollients on infants with atopic dermatitis showed that the emollient group has a lower skin pH and a more diverse microbiome.22 In a 2016 study on the impact of acute treatment with topical skin cleansers on the cutaneous microbiome, investigators evaluated multiple common skin cleansers in the washing of human forearms. Group A Streptococcus growth was reduced after washing with soaps infused with such antimicrobial compounds as benzalkonium chloride or triclocarban. The researchers stipulated that much more research is necessary to ascertain the effects of chronic washing as well as the that role skin care products may play in skin homeostasis or dysbiosis in some individuals.23
In a 2017 analysis of the effects of cosmetics on the skin microbiome of facial cheeks with high- and low-hydration levels over 4 weeks, Lee et al. found that bacterial diversity was higher in the low-hydration group, with increases in both observed after the use of cosmetics. The high-hydration group showed a greater supply of Propionibacterium. Cosmetic use was found not to have caused a shift in bacterial communities in the low-hydration group.24
Conclusion
We are in the early stages as we strive to learn more about the microbiome to leverage such knowledge to improve skin health. In the meantime, there is not enough evidence to suggest the use of any oral or topical prebiotics or probiotics to improve skin health. In fact, we may be causing harm by lessening diversity. The New York Times recently published an article called “The Problem with Probiotics” that referenced a JAMA Internal Medicine article entitled “Probiotic Safety – No Guarantees.”25 I recommend that you read those. Next month, I will look more closely at microbiome research pertaining to skin disease.
Dr. Baumann is a private practice dermatologist, researcher, author and entrepreneur who practices in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote two textbooks: “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002), and “Cosmeceuticals and Cosmetic Ingredients,” (New York: McGraw-Hill, 2014), and a New York Times Best Sellers book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Evolus, Galderma, and Revance. She is the founder and CEO of Skin Type Solutions Franchise Systems LLC.
References
1. Dréno B et al. J Eur Acad Dermatol Venereol. 2016 Dec;30(12):2038-47.
2. O’Neill CA et al. Bioessays. 2016 Nov;38(11):1167-76.
3. Kong HH. Trends Mol Med. 2011 Jun;17(6):320-8.
4. Kong HH et al. J Invest Dermatol. 2017 May;137(5):e119-22.
5. Gallo RL. J Invest Dermatol. 2017 Jun;137(6):1213-4.
6. Byrd AL et al. Nat Rev Microbiol. 2018 Mar;16(3):143-55.
7. Grice EA et al. Nat Rev Microbiol. 2011 Apr;9(4):244-53.
8. Rodrigues Hoffmann A. Vet Dermatol. 2017 Feb;28(1):60-e15.
9. Moestrup KS et al. J Invest Dermatol. 2018 May;138(5):1225-8.
10. Prescott SL et al. World Allergy Organ J. 2017 Aug 22;10(1):29.
11. Costello EK et al. Science. 2009 Dec 18;326(5960):1694-7.
12. Zeeuwen PL et al. Genome Biol. 2012 Nov 15;13(11):R101.
13. Mukherjee S et al. Sci Rep. 2016 Oct 27;6:36062.
14. Oh J et al. Genome Med. 2012 Oct 10;4(10):77.
15. Ross AA et al. mSystems. 2017 Jul 20;2(4).
16. Blázquez AB et al. Transl Res. 2017 Jan;179:199-203.
17. Rock R et al. Open Forum Infect Dis. 2017 Oct;4(1):S232.
18. Baldwin HE et al. J Drugs Dermatol. 2017 Jan 1;16(1):12-8.
19. Byrd AL et al. Nat Rev Microbiol. 2018 Mar;16(3):143-55.
20. Maguire M et al. Arch Dermatol Res. 2017 Aug;309(6):411-21.
21. Kong HH et al. Genome Res. 2012 May;22(5):850-9.
22. Glatz M et al. PLoS One. 2018 Feb 28;13(2):e0192443.
23. Two AM et al. J Invest Dermatol. 2016 Oct;136(10):1950-4.
24. Lee HJ et al. MicrobiologyOpen. 2018 Apr;7(2):e00557. doi: 10.1002/mbo3.557.
25. Cohen PA. JAMA Intern Med. 2018 Sep 17. doi: 10.1001/jamainternmed.2018.5403.
It may not seem intuitive, but to understand some of the new skin care claims, you need to know a bit about the gut microbiome and its role in skin health. The The gut and skin play a balancing act between beneficial, neutral, and harmful flora that are interrelated with the innate and adaptive immune systems.1 The skin and gut seem to be intertwined and express several comorbidities.2 In this column, the focus is on the cutaneous microbiome’s role in skin health. To understand the cosmeceutical claims about pre- and probiotics, you first need to familiarize yourself with skin microbiome science. The skin-gut nexus will be discussed in next month’s column, which will address the role of the skin microbiome in skin diseases.
Why is the microbiome such a hot topic?
Genetic sequencing has spurred advances in the study of the microbiome and has provided intriguing clues that the gut and skin microbiome have influences on each other. Sequencing assays that focus on bacterial 16S ribosomal RNA genes have been used by investigators to distinguish and describe the wide variety of resident and transient microorganisms on the skin and elucidate their roles in skin health and disease.1 Genomic sequencing has identified species in the skin and gut that were not found previously by cultivating microbial isolates.3,4 Advances in technologies such as whole-genome shotgun sequencing, metagenomics, and functional metabolomics will further contribute to our understanding of the effects of the skin microbiome on skin health and skin type. Of course, many supplement and cosmeceutical companies have jumped on this bandwagon prematurely and claim that their products increase “good bacteria while diminishing bad bacteria.” While there are interesting data that have emerged, we still cannot say which bacteria are “good” and ‘bad” as far as the skin is concerned – with a few exceptions that we have known all along. For example, Cutibacterium acnes and Staphylococcus aureus still remain in the undesirable category. (P. acnes has been renamed and now is officially referred to as C. acnes.) While it is premature to recommend probiotic– or prebiotic–containing cosmeceuticals, your patients will ask you about them. New studies about rosacea and the microbiome have generated a lot of patient questions in my practice, so I am writing several blogs about how to answer patient questions, which can be found at STSFranchise.com/blog. I’m also educating consumers on Facebook and Instagram @skintypesolutions so that they will not be taken advantage of by the too early “pseudoscience.” So now that you have heard that it is too early to recommend pre- and probiotic skin care to target skin issues, let’s look at the science that does exist.
Terminology
- Microbiome: Microbes that live in a particular environment or biome.
- Microbiota: The collection of living microbes that live in or on an environment. This term includes the microorganisms only and not the characteristics of their environment.
- Prebiotics: A nondigestible food ingredient that promotes the growth of microorganisms in the intestines. These can promote the growth of beneficial or harmful microorganisms. Think of them as a type of “fertilizer” for the microbiome.
- Probiotics: Living microorganisms that can provide beneficial qualities when used orally or topically. What probiotics are not? Microbes naturally found in your body and on your skin; microbes that are no longer alive; fermented foods that contain an unknown amount of bacteria.
Skin surface area
Richard Gallo, MD, a dermatologist from the University of California, San Diego, who is a leader in the microbiome field of study, says that estimates of the cutaneous microbiome’s impact on human health via skin have failed to acknowledge the inner follicular surface, thus drastically undervaluing the potential of the cutaneous microbiome to influence systemic health.5 He suggests that the surface area of skin has been miscalculated as measuring 2 m2 because it is considered a flat surface. This ignores the plethora of hair follicles and sweat ducts that significantly broaden the epithelial surface to measure closer to 25 m2 and underscores that the expansive skin microbiome is much larger than previously recognized.5 Taking the hair follicle surface area into account, the skin has vast space to harbor various organisms and microbiome environments. What our patients use on their skin certainly influences these environments. The key is trying to figure out how to manipulate the microbiome to our patient’s advantage.
Microbes have environmental preferences
Different microbial species thrive on particular regions of the diverse topography of the expansive surface area and choose their preferred environments from among sebaceous or nonsebaceous, hairy or smooth, moist or dry, and creased or noncreased areas.6,7 Other host factors that affect which microorganisms colonize the skin include hair follicle thickness, age, sex, diet (especially high fat and sugar intake), climate, occupation, and personal hygiene.7-10 Gene sequencing has revealed that these variations are partially because of factors such as ultraviolet exposure, pH, and temperature.4,6,11 For example, C. acnes has been found to be more prevalent in highly sebaceous sites on the head and upper torso.4 In general, Propionibacteriaceae (Cutibacterium) prefer sebaceous areas, whereas Corynebacteriaceae and Staphylococcaceae prevail in moist regions, such as the navel or axilla. Dry areas host the widest diversity of microbes, including Corynebacterium, Staphylococcus, and Streptococcus species.1,7,12
Impact of sebum and skin hydration on microbiome
In 2016, Mukherjee et al. measured sebum and hydration from the forehead and cheeks of 30 healthy female volunteers in a study that tested the hypothesis that differences in sebum and hydration levels in specific facial areas account for interindividual variation in facial skin microbiome. They found that the most significant predictor of microbiome composition was cheek sebum level, followed by forehead hydration level, while cheek hydration and forehead sebum levels were not predictive. The prevalence of Actinobacteria/Propionibacterium rose, while microbiome diversity diminished with an increase in cheek sebum, with such trends reversed in relation to forehead hydration. The investigators concluded that site-specific sebum and water levels impact the nature and diversity of the facial skin microbiome.13
Lability of the cutaneous microbiome
The skin microbiome changes during various times of life. For example, in puberty, more lipophilic species such as Propionibacteriaceae and Cornebacteriaceae predominate, while prior to puberty there is a preponderance of Firmicutes, Bacteroidetes, and Proteobacteria.4,14 However, in the absence of lifestyle changes, cutaneous microbial communities have been found through longitudinal studies to be relatively stable over a 2-year period.6 A person’s skin microbiome is subject to influence from an adjacent skin microbiome, such as between cohabiting couples or the influence of breastfeeding mothers.15 It is never too early to consider the role of the microbiome in health and disease. For example, infant microbiomes play a role in eczema and the atopic march.16 For this reason, those of us who treat children need to be familiar with studies that have demonstrate how the cutaneous microbiome is affected by childbirth delivery method, breastfeeding, the mother’s diet antibiotic use during pregnancy and breastfeeding.4,17
Microbiome effects on skin function
The skin barrier, a bilayer lipid-laden membrane that surrounds keratinocytes and prevents transepidermal water loss, is affected by resident microbial communities and has been shown by research to be influenced by the volume and diversity of such microbes.18 Organisms on the skin’s surface play an important role in communicating with and educating the cutaneous arm of the immune system.19 In 2017, Maguire and Maguire reviewed recent studies of the gut and skin microbiomes and suggested that Nitrobacter, Lactobacillus, and Bifidobacterium can improve skin health and could be useful bacterial adjuvants in a probiotic and prebiotic strategy in homeostatic renormalization when skin health is compromised.20Nitrobacter has displayed antifungal activity against dermatophytes and Staphylococcus; Lactobacillus has exhibited anti-inflammatory effects and was shown to improve adult acne in a small study; Bifidobacterium combined with Lactobacillus lowered the incidence of atopic eczema in early childhood; and Bifidobacterium and the prebiotic galacto-oligosaccharide prevented hydration level losses in the stratum corneum among other beneficial effects in a double-blind, placebo-controlled, randomized trial.20
Microbiome diversity is key
Microbes interact, collaborate, and oppose one another while exerting influence and being affected by the host. Effective communication among the innate and adaptive parts of the immune system, epithelial cells, and cutaneous microbiota is essential for optimal functioning of the skin.6,7 Studies on subjects with atopic dermatitis showed a strong association between decreased diversity and increased disease severity. This suggests that a diverse microbiome is associated with skin health.21 For this reason, use of pre- and probiotics for skin issues is discouraged at this time. If we replace the normal diverse flora with one organism, we do not yet know the consequences. It is much more likely that successful treatments in the future will contain a diverse group of organisms.
Cosmeceutical effects on the skin microbiome
Cleansing and use of emollients certainly affect the skin biome, but we do not yet know to what extent. A study that looked at the effects of emollients on infants with atopic dermatitis showed that the emollient group has a lower skin pH and a more diverse microbiome.22 In a 2016 study on the impact of acute treatment with topical skin cleansers on the cutaneous microbiome, investigators evaluated multiple common skin cleansers in the washing of human forearms. Group A Streptococcus growth was reduced after washing with soaps infused with such antimicrobial compounds as benzalkonium chloride or triclocarban. The researchers stipulated that much more research is necessary to ascertain the effects of chronic washing as well as the that role skin care products may play in skin homeostasis or dysbiosis in some individuals.23
In a 2017 analysis of the effects of cosmetics on the skin microbiome of facial cheeks with high- and low-hydration levels over 4 weeks, Lee et al. found that bacterial diversity was higher in the low-hydration group, with increases in both observed after the use of cosmetics. The high-hydration group showed a greater supply of Propionibacterium. Cosmetic use was found not to have caused a shift in bacterial communities in the low-hydration group.24
Conclusion
We are in the early stages as we strive to learn more about the microbiome to leverage such knowledge to improve skin health. In the meantime, there is not enough evidence to suggest the use of any oral or topical prebiotics or probiotics to improve skin health. In fact, we may be causing harm by lessening diversity. The New York Times recently published an article called “The Problem with Probiotics” that referenced a JAMA Internal Medicine article entitled “Probiotic Safety – No Guarantees.”25 I recommend that you read those. Next month, I will look more closely at microbiome research pertaining to skin disease.
Dr. Baumann is a private practice dermatologist, researcher, author and entrepreneur who practices in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote two textbooks: “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002), and “Cosmeceuticals and Cosmetic Ingredients,” (New York: McGraw-Hill, 2014), and a New York Times Best Sellers book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Evolus, Galderma, and Revance. She is the founder and CEO of Skin Type Solutions Franchise Systems LLC.
References
1. Dréno B et al. J Eur Acad Dermatol Venereol. 2016 Dec;30(12):2038-47.
2. O’Neill CA et al. Bioessays. 2016 Nov;38(11):1167-76.
3. Kong HH. Trends Mol Med. 2011 Jun;17(6):320-8.
4. Kong HH et al. J Invest Dermatol. 2017 May;137(5):e119-22.
5. Gallo RL. J Invest Dermatol. 2017 Jun;137(6):1213-4.
6. Byrd AL et al. Nat Rev Microbiol. 2018 Mar;16(3):143-55.
7. Grice EA et al. Nat Rev Microbiol. 2011 Apr;9(4):244-53.
8. Rodrigues Hoffmann A. Vet Dermatol. 2017 Feb;28(1):60-e15.
9. Moestrup KS et al. J Invest Dermatol. 2018 May;138(5):1225-8.
10. Prescott SL et al. World Allergy Organ J. 2017 Aug 22;10(1):29.
11. Costello EK et al. Science. 2009 Dec 18;326(5960):1694-7.
12. Zeeuwen PL et al. Genome Biol. 2012 Nov 15;13(11):R101.
13. Mukherjee S et al. Sci Rep. 2016 Oct 27;6:36062.
14. Oh J et al. Genome Med. 2012 Oct 10;4(10):77.
15. Ross AA et al. mSystems. 2017 Jul 20;2(4).
16. Blázquez AB et al. Transl Res. 2017 Jan;179:199-203.
17. Rock R et al. Open Forum Infect Dis. 2017 Oct;4(1):S232.
18. Baldwin HE et al. J Drugs Dermatol. 2017 Jan 1;16(1):12-8.
19. Byrd AL et al. Nat Rev Microbiol. 2018 Mar;16(3):143-55.
20. Maguire M et al. Arch Dermatol Res. 2017 Aug;309(6):411-21.
21. Kong HH et al. Genome Res. 2012 May;22(5):850-9.
22. Glatz M et al. PLoS One. 2018 Feb 28;13(2):e0192443.
23. Two AM et al. J Invest Dermatol. 2016 Oct;136(10):1950-4.
24. Lee HJ et al. MicrobiologyOpen. 2018 Apr;7(2):e00557. doi: 10.1002/mbo3.557.
25. Cohen PA. JAMA Intern Med. 2018 Sep 17. doi: 10.1001/jamainternmed.2018.5403.
It may not seem intuitive, but to understand some of the new skin care claims, you need to know a bit about the gut microbiome and its role in skin health. The The gut and skin play a balancing act between beneficial, neutral, and harmful flora that are interrelated with the innate and adaptive immune systems.1 The skin and gut seem to be intertwined and express several comorbidities.2 In this column, the focus is on the cutaneous microbiome’s role in skin health. To understand the cosmeceutical claims about pre- and probiotics, you first need to familiarize yourself with skin microbiome science. The skin-gut nexus will be discussed in next month’s column, which will address the role of the skin microbiome in skin diseases.
Why is the microbiome such a hot topic?
Genetic sequencing has spurred advances in the study of the microbiome and has provided intriguing clues that the gut and skin microbiome have influences on each other. Sequencing assays that focus on bacterial 16S ribosomal RNA genes have been used by investigators to distinguish and describe the wide variety of resident and transient microorganisms on the skin and elucidate their roles in skin health and disease.1 Genomic sequencing has identified species in the skin and gut that were not found previously by cultivating microbial isolates.3,4 Advances in technologies such as whole-genome shotgun sequencing, metagenomics, and functional metabolomics will further contribute to our understanding of the effects of the skin microbiome on skin health and skin type. Of course, many supplement and cosmeceutical companies have jumped on this bandwagon prematurely and claim that their products increase “good bacteria while diminishing bad bacteria.” While there are interesting data that have emerged, we still cannot say which bacteria are “good” and ‘bad” as far as the skin is concerned – with a few exceptions that we have known all along. For example, Cutibacterium acnes and Staphylococcus aureus still remain in the undesirable category. (P. acnes has been renamed and now is officially referred to as C. acnes.) While it is premature to recommend probiotic– or prebiotic–containing cosmeceuticals, your patients will ask you about them. New studies about rosacea and the microbiome have generated a lot of patient questions in my practice, so I am writing several blogs about how to answer patient questions, which can be found at STSFranchise.com/blog. I’m also educating consumers on Facebook and Instagram @skintypesolutions so that they will not be taken advantage of by the too early “pseudoscience.” So now that you have heard that it is too early to recommend pre- and probiotic skin care to target skin issues, let’s look at the science that does exist.
Terminology
- Microbiome: Microbes that live in a particular environment or biome.
- Microbiota: The collection of living microbes that live in or on an environment. This term includes the microorganisms only and not the characteristics of their environment.
- Prebiotics: A nondigestible food ingredient that promotes the growth of microorganisms in the intestines. These can promote the growth of beneficial or harmful microorganisms. Think of them as a type of “fertilizer” for the microbiome.
- Probiotics: Living microorganisms that can provide beneficial qualities when used orally or topically. What probiotics are not? Microbes naturally found in your body and on your skin; microbes that are no longer alive; fermented foods that contain an unknown amount of bacteria.
Skin surface area
Richard Gallo, MD, a dermatologist from the University of California, San Diego, who is a leader in the microbiome field of study, says that estimates of the cutaneous microbiome’s impact on human health via skin have failed to acknowledge the inner follicular surface, thus drastically undervaluing the potential of the cutaneous microbiome to influence systemic health.5 He suggests that the surface area of skin has been miscalculated as measuring 2 m2 because it is considered a flat surface. This ignores the plethora of hair follicles and sweat ducts that significantly broaden the epithelial surface to measure closer to 25 m2 and underscores that the expansive skin microbiome is much larger than previously recognized.5 Taking the hair follicle surface area into account, the skin has vast space to harbor various organisms and microbiome environments. What our patients use on their skin certainly influences these environments. The key is trying to figure out how to manipulate the microbiome to our patient’s advantage.
Microbes have environmental preferences
Different microbial species thrive on particular regions of the diverse topography of the expansive surface area and choose their preferred environments from among sebaceous or nonsebaceous, hairy or smooth, moist or dry, and creased or noncreased areas.6,7 Other host factors that affect which microorganisms colonize the skin include hair follicle thickness, age, sex, diet (especially high fat and sugar intake), climate, occupation, and personal hygiene.7-10 Gene sequencing has revealed that these variations are partially because of factors such as ultraviolet exposure, pH, and temperature.4,6,11 For example, C. acnes has been found to be more prevalent in highly sebaceous sites on the head and upper torso.4 In general, Propionibacteriaceae (Cutibacterium) prefer sebaceous areas, whereas Corynebacteriaceae and Staphylococcaceae prevail in moist regions, such as the navel or axilla. Dry areas host the widest diversity of microbes, including Corynebacterium, Staphylococcus, and Streptococcus species.1,7,12
Impact of sebum and skin hydration on microbiome
In 2016, Mukherjee et al. measured sebum and hydration from the forehead and cheeks of 30 healthy female volunteers in a study that tested the hypothesis that differences in sebum and hydration levels in specific facial areas account for interindividual variation in facial skin microbiome. They found that the most significant predictor of microbiome composition was cheek sebum level, followed by forehead hydration level, while cheek hydration and forehead sebum levels were not predictive. The prevalence of Actinobacteria/Propionibacterium rose, while microbiome diversity diminished with an increase in cheek sebum, with such trends reversed in relation to forehead hydration. The investigators concluded that site-specific sebum and water levels impact the nature and diversity of the facial skin microbiome.13
Lability of the cutaneous microbiome
The skin microbiome changes during various times of life. For example, in puberty, more lipophilic species such as Propionibacteriaceae and Cornebacteriaceae predominate, while prior to puberty there is a preponderance of Firmicutes, Bacteroidetes, and Proteobacteria.4,14 However, in the absence of lifestyle changes, cutaneous microbial communities have been found through longitudinal studies to be relatively stable over a 2-year period.6 A person’s skin microbiome is subject to influence from an adjacent skin microbiome, such as between cohabiting couples or the influence of breastfeeding mothers.15 It is never too early to consider the role of the microbiome in health and disease. For example, infant microbiomes play a role in eczema and the atopic march.16 For this reason, those of us who treat children need to be familiar with studies that have demonstrate how the cutaneous microbiome is affected by childbirth delivery method, breastfeeding, the mother’s diet antibiotic use during pregnancy and breastfeeding.4,17
Microbiome effects on skin function
The skin barrier, a bilayer lipid-laden membrane that surrounds keratinocytes and prevents transepidermal water loss, is affected by resident microbial communities and has been shown by research to be influenced by the volume and diversity of such microbes.18 Organisms on the skin’s surface play an important role in communicating with and educating the cutaneous arm of the immune system.19 In 2017, Maguire and Maguire reviewed recent studies of the gut and skin microbiomes and suggested that Nitrobacter, Lactobacillus, and Bifidobacterium can improve skin health and could be useful bacterial adjuvants in a probiotic and prebiotic strategy in homeostatic renormalization when skin health is compromised.20Nitrobacter has displayed antifungal activity against dermatophytes and Staphylococcus; Lactobacillus has exhibited anti-inflammatory effects and was shown to improve adult acne in a small study; Bifidobacterium combined with Lactobacillus lowered the incidence of atopic eczema in early childhood; and Bifidobacterium and the prebiotic galacto-oligosaccharide prevented hydration level losses in the stratum corneum among other beneficial effects in a double-blind, placebo-controlled, randomized trial.20
Microbiome diversity is key
Microbes interact, collaborate, and oppose one another while exerting influence and being affected by the host. Effective communication among the innate and adaptive parts of the immune system, epithelial cells, and cutaneous microbiota is essential for optimal functioning of the skin.6,7 Studies on subjects with atopic dermatitis showed a strong association between decreased diversity and increased disease severity. This suggests that a diverse microbiome is associated with skin health.21 For this reason, use of pre- and probiotics for skin issues is discouraged at this time. If we replace the normal diverse flora with one organism, we do not yet know the consequences. It is much more likely that successful treatments in the future will contain a diverse group of organisms.
Cosmeceutical effects on the skin microbiome
Cleansing and use of emollients certainly affect the skin biome, but we do not yet know to what extent. A study that looked at the effects of emollients on infants with atopic dermatitis showed that the emollient group has a lower skin pH and a more diverse microbiome.22 In a 2016 study on the impact of acute treatment with topical skin cleansers on the cutaneous microbiome, investigators evaluated multiple common skin cleansers in the washing of human forearms. Group A Streptococcus growth was reduced after washing with soaps infused with such antimicrobial compounds as benzalkonium chloride or triclocarban. The researchers stipulated that much more research is necessary to ascertain the effects of chronic washing as well as the that role skin care products may play in skin homeostasis or dysbiosis in some individuals.23
In a 2017 analysis of the effects of cosmetics on the skin microbiome of facial cheeks with high- and low-hydration levels over 4 weeks, Lee et al. found that bacterial diversity was higher in the low-hydration group, with increases in both observed after the use of cosmetics. The high-hydration group showed a greater supply of Propionibacterium. Cosmetic use was found not to have caused a shift in bacterial communities in the low-hydration group.24
Conclusion
We are in the early stages as we strive to learn more about the microbiome to leverage such knowledge to improve skin health. In the meantime, there is not enough evidence to suggest the use of any oral or topical prebiotics or probiotics to improve skin health. In fact, we may be causing harm by lessening diversity. The New York Times recently published an article called “The Problem with Probiotics” that referenced a JAMA Internal Medicine article entitled “Probiotic Safety – No Guarantees.”25 I recommend that you read those. Next month, I will look more closely at microbiome research pertaining to skin disease.
Dr. Baumann is a private practice dermatologist, researcher, author and entrepreneur who practices in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote two textbooks: “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002), and “Cosmeceuticals and Cosmetic Ingredients,” (New York: McGraw-Hill, 2014), and a New York Times Best Sellers book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Evolus, Galderma, and Revance. She is the founder and CEO of Skin Type Solutions Franchise Systems LLC.
References
1. Dréno B et al. J Eur Acad Dermatol Venereol. 2016 Dec;30(12):2038-47.
2. O’Neill CA et al. Bioessays. 2016 Nov;38(11):1167-76.
3. Kong HH. Trends Mol Med. 2011 Jun;17(6):320-8.
4. Kong HH et al. J Invest Dermatol. 2017 May;137(5):e119-22.
5. Gallo RL. J Invest Dermatol. 2017 Jun;137(6):1213-4.
6. Byrd AL et al. Nat Rev Microbiol. 2018 Mar;16(3):143-55.
7. Grice EA et al. Nat Rev Microbiol. 2011 Apr;9(4):244-53.
8. Rodrigues Hoffmann A. Vet Dermatol. 2017 Feb;28(1):60-e15.
9. Moestrup KS et al. J Invest Dermatol. 2018 May;138(5):1225-8.
10. Prescott SL et al. World Allergy Organ J. 2017 Aug 22;10(1):29.
11. Costello EK et al. Science. 2009 Dec 18;326(5960):1694-7.
12. Zeeuwen PL et al. Genome Biol. 2012 Nov 15;13(11):R101.
13. Mukherjee S et al. Sci Rep. 2016 Oct 27;6:36062.
14. Oh J et al. Genome Med. 2012 Oct 10;4(10):77.
15. Ross AA et al. mSystems. 2017 Jul 20;2(4).
16. Blázquez AB et al. Transl Res. 2017 Jan;179:199-203.
17. Rock R et al. Open Forum Infect Dis. 2017 Oct;4(1):S232.
18. Baldwin HE et al. J Drugs Dermatol. 2017 Jan 1;16(1):12-8.
19. Byrd AL et al. Nat Rev Microbiol. 2018 Mar;16(3):143-55.
20. Maguire M et al. Arch Dermatol Res. 2017 Aug;309(6):411-21.
21. Kong HH et al. Genome Res. 2012 May;22(5):850-9.
22. Glatz M et al. PLoS One. 2018 Feb 28;13(2):e0192443.
23. Two AM et al. J Invest Dermatol. 2016 Oct;136(10):1950-4.
24. Lee HJ et al. MicrobiologyOpen. 2018 Apr;7(2):e00557. doi: 10.1002/mbo3.557.
25. Cohen PA. JAMA Intern Med. 2018 Sep 17. doi: 10.1001/jamainternmed.2018.5403.