The effect of sunscreen on the efficacy of insect repellent: a clinical trial.

Sunscreen loses efficacy when used with the insect repellent N,N -diethyl-3-methylbenzamide (diethyltoluamide; deet). A previous study demonstrated a 33.3% decrease in sun protection factor when insect repellent and sunscreen were applied sequentially to the skin. The purpose of this study was to determine whether the efficacy of insect repellent is affected by two different formulations of sunscreen. The combination of sunscreen and insect repellent was tested in 8 groups: a control group (no sunscreen or insect repellent), sunscreen alone (two groups [gel and cream]), insect repellent alone, insect repellent applied before sunscreen (two groups), and insect repellent applied after sunscreen (two groups). The results of this study showed that insect repellent has the same efficacy even when sunscreen is applied with it. This indicates that in the formulations tested, sunscreen does not reduce the efficacy of insect repellent.