Effectiveness of a Repellent Containing DEET and EBAAP for Preventing Tick Bites

Abstract

Topical repellents can provide effective personal protection from tick-borne diseases by preventing the attachment of ticks. The goal of this study was to assess the effectiveness of a commercially available repellent spray containing both N,N-diethyl-3-methylbenzamide, previously known as N,N-diethyl-m-toluamide (DEET), and ethyl-butylacetylaminopropionate (EBAAP) against tick bites in a population at risk in Switzerland under real-life conditions. The effectiveness of an insect repellent spray containing both DEET and EBAAP was evaluated in a randomized, double-blind, placebo-controlled field study. The study, requiring simple application of the repellent to exposed skin, was carried out on 276 forestry workers and orienteers under everyday conditions in Switzerland from May to September 1999. We measured total effectiveness of the repellent by the following formula: percentage effectiveness = 100 x (T(P) - T(R))/T(P), where T(P) and T(R) were the average number of ticks per hour spent in wooded areas for the repellent and placebo groups, respectively. The average number of tick bites per hour of exposure to wooded areas differed significantly between the placebo (n = 138) and repellent (n = 138) groups, 0.17 vs 0.10 (P < .05). Total repellent effectiveness against tick attachment was 41.1% (95% CI, 2.5-79.6). On the arms, an effectiveness of 66% (95% CI, 17.3-114.7) was observed. No significant difference in the average number of unattached ticks could be found. This study found that an easily applied repellent is moderately effective in reducing the risk of tick bites.