DEET is the most effective mosquito repellent

ABSTRACT

BACKGROUND: The search for optimal protection against mosquitoes is particularly timely, with West Nile virus infection becoming more of a threat in the United States. Internationally, malaria is the primary infectious disease transmitted by mosquito. Mosquito-transmitted diseases are responsible for 1 in 17 deaths worldwide. New repellents have come out on the market, but their relative effectiveness has not been delineated.

POPULATION STUDIED: The researchers recruited 15 volunteers from the staff of the Medical Entomology Laboratory at the University of Florida (10 were women). Age, ethnicity, and medical histories were not reported.

STUDY DESIGN AND VALIDITY: The goal of the researchers was to compare the effectiveness of 16 products containing 7 botanical repellents. The products included those containing 4 different concentrations of DEET (N, N-diethyl-3-methylbenzamide), 2% soybean oil, 5 different formulations of citronella, and IR3535; in addition, 3 repellentimpregnated wristbands were tested. All products are nationally available in the United States. The study used an “arm-in-cage” design; volunteers inserted their repellent-treated bare arms into a cage with 10 hungry, disease-free female mosquitoes. This low mosquito density environment was considered to be similar to typical exposures. The order of tests was randomized and the volunteers were blinded to the repellent used. Hours of light and dark, humidity, and temperature were constant. Each repellent was tested 3 times on each subject. No more than 1 repellent was tested per day. The repellents were applied according to the instructions on the product’s label. Subjects inserted an arm into the cage for 1 minute every 5 minutes. If they were not bitten after 20 minutes, the insertion interval was changed to every 15 minutes. The test was stopped with the first bite. The study was funded by the State of Florida.

OUTCOMES MEASURED: Time to the first mosquito bite using different repellents in a controlled situation.

RESULTS: DEET was the clear winner in these tests, especially in the highest concentration. The highest DEET concentration (23.8%) protected for an average of 301.5 ± 37.6 minutes. This concentration, which was alcohol based, protected significantly longer than the 20% controlled-release formulation (245.5 ± 31.8 minutes). Only DEET-containing repellents protected longer than 1.5 hours. The soybean oil repellent protected similar to the lowest concentration of DEET (94.6 vs 88 minutes, respectively). The wristbands were essentially not effective. Citronella-based lotions worked for only 10.3 ± 7.9 minutes at best.

ABSTRACT

BACKGROUND: The search for optimal protection against mosquitoes is particularly timely, with West Nile virus infection becoming more of a threat in the United States. Internationally, malaria is the primary infectious disease transmitted by mosquito. Mosquito-transmitted diseases are responsible for 1 in 17 deaths worldwide. New repellents have come out on the market, but their relative effectiveness has not been delineated.

POPULATION STUDIED: The researchers recruited 15 volunteers from the staff of the Medical Entomology Laboratory at the University of Florida (10 were women). Age, ethnicity, and medical histories were not reported.

STUDY DESIGN AND VALIDITY: The goal of the researchers was to compare the effectiveness of 16 products containing 7 botanical repellents. The products included those containing 4 different concentrations of DEET (N, N-diethyl-3-methylbenzamide), 2% soybean oil, 5 different formulations of citronella, and IR3535; in addition, 3 repellentimpregnated wristbands were tested. All products are nationally available in the United States. The study used an “arm-in-cage” design; volunteers inserted their repellent-treated bare arms into a cage with 10 hungry, disease-free female mosquitoes. This low mosquito density environment was considered to be similar to typical exposures. The order of tests was randomized and the volunteers were blinded to the repellent used. Hours of light and dark, humidity, and temperature were constant. Each repellent was tested 3 times on each subject. No more than 1 repellent was tested per day. The repellents were applied according to the instructions on the product’s label. Subjects inserted an arm into the cage for 1 minute every 5 minutes. If they were not bitten after 20 minutes, the insertion interval was changed to every 15 minutes. The test was stopped with the first bite. The study was funded by the State of Florida.

OUTCOMES MEASURED: Time to the first mosquito bite using different repellents in a controlled situation.

RESULTS: DEET was the clear winner in these tests, especially in the highest concentration. The highest DEET concentration (23.8%) protected for an average of 301.5 ± 37.6 minutes. This concentration, which was alcohol based, protected significantly longer than the 20% controlled-release formulation (245.5 ± 31.8 minutes). Only DEET-containing repellents protected longer than 1.5 hours. The soybean oil repellent protected similar to the lowest concentration of DEET (94.6 vs 88 minutes, respectively). The wristbands were essentially not effective. Citronella-based lotions worked for only 10.3 ± 7.9 minutes at best.

ABSTRACT

BACKGROUND: The search for optimal protection against mosquitoes is particularly timely, with West Nile virus infection becoming more of a threat in the United States. Internationally, malaria is the primary infectious disease transmitted by mosquito. Mosquito-transmitted diseases are responsible for 1 in 17 deaths worldwide. New repellents have come out on the market, but their relative effectiveness has not been delineated.

POPULATION STUDIED: The researchers recruited 15 volunteers from the staff of the Medical Entomology Laboratory at the University of Florida (10 were women). Age, ethnicity, and medical histories were not reported.

STUDY DESIGN AND VALIDITY: The goal of the researchers was to compare the effectiveness of 16 products containing 7 botanical repellents. The products included those containing 4 different concentrations of DEET (N, N-diethyl-3-methylbenzamide), 2% soybean oil, 5 different formulations of citronella, and IR3535; in addition, 3 repellentimpregnated wristbands were tested. All products are nationally available in the United States. The study used an “arm-in-cage” design; volunteers inserted their repellent-treated bare arms into a cage with 10 hungry, disease-free female mosquitoes. This low mosquito density environment was considered to be similar to typical exposures. The order of tests was randomized and the volunteers were blinded to the repellent used. Hours of light and dark, humidity, and temperature were constant. Each repellent was tested 3 times on each subject. No more than 1 repellent was tested per day. The repellents were applied according to the instructions on the product’s label. Subjects inserted an arm into the cage for 1 minute every 5 minutes. If they were not bitten after 20 minutes, the insertion interval was changed to every 15 minutes. The test was stopped with the first bite. The study was funded by the State of Florida.

OUTCOMES MEASURED: Time to the first mosquito bite using different repellents in a controlled situation.

RESULTS: DEET was the clear winner in these tests, especially in the highest concentration. The highest DEET concentration (23.8%) protected for an average of 301.5 ± 37.6 minutes. This concentration, which was alcohol based, protected significantly longer than the 20% controlled-release formulation (245.5 ± 31.8 minutes). Only DEET-containing repellents protected longer than 1.5 hours. The soybean oil repellent protected similar to the lowest concentration of DEET (94.6 vs 88 minutes, respectively). The wristbands were essentially not effective. Citronella-based lotions worked for only 10.3 ± 7.9 minutes at best.