Insect Repellents and Mosquito Bites Comparative Efficacy of Insect Repellents against Mosquito Bites

Background. The worldwide threat of arthropod transmitted diseased, with their associated morbidity and mortality, underscores the need for effective insect repellents. Multiple chemical, botanical, and “alternative” repellent products are marketed to consumers. We sought to determine which products available in the United States provide reliable and prolonged complete protection from mosquito bites. Methods. We conducted studies involving 15 volunteers to test the relative efficacy of seven botanical insect repellents; four products containing N,N-diethyl-m-toluamide (DEET); a repellent containing IR3535; three repellent-impregnated wristbands; and a moisturizer that is commonly claimed to have repellent effects. These products were tested in a controlled laboratory environment in which the species of the mosquitoes, their age, their degree of hunger, the humidity, the temperature, and the light – dark cycle were all kept constant. Results. DEET – based products provided complete protection for the longest duration. Higher concentrations of DEET provided longer-lasting protection. A formulation containing 23.8 percent DEET had a mean complete protection time of 301.5 minutes. The IR3535-based repellent protected for an average of 22.9 minutes. All other botanical repellents we tested provided protection for a men duration of less than 20 minutes. Repellentimpregnated wristbands offered no protection. Conclusions. Currently available nonDEET repellents do not provide protection for durations similar to those of DEET-based repellents and cannot be relied on to provide prolonged protection in environments where mosquito-borne diseased are a substantial threat. (N Engl J Med 2002;347:13-8.) INSECT – TRANSMITTED disease remains a major source of illness and death worldwide. Mosquitoes alone transmit disease to more than 700 million persons annually. Malaria kills 3 million persons each year, including 1 child every 30 seconds. Protection from arthropod bites is best achieved by avoiding infested habitats, wearing protective clothing, and using insect repellent. In many circumstances, applying repellent to the skin may be the only feasible way to protect against insect bites. Given that a single bite from and infected arthropod can result in transmission of disease, it is important to know which repellent products can be relied on to provide predictable and prolonged protection from insect bites. Commercially available insect repellents can be divided into two categories – synthetic chemicals and plant derived essential oils. The best known chemical insect repellent is N, N-diethyl-mtoluamide (DEET). Many consumers, reluctant to apply DEET to their skin, deliberately seek out other repellent products. We compared the efficacy of readily available alternatives to DEET – based repellents in a controlled laboratory environment.