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Deet Insect Repellent May Be Toxic

DEET insect repellents and mosquitoes

DEET, the active ingredient in many insect repellents that are used by more than 200 million people each year, works like the paralyzing nerve gases designed for warfare. The warfare association is understandable, given that the toxin was originally developed by the US Army in 1946.

DEET (N,N-diethyl-meta-toluamide) was registered by the Environmental Protection Agency (EPA) for use by the general population in 1957. The toxin is used to repel biting insects such as mosquitoes, which can carry West Nile virus and malaria, and ticks, including those that are known to carry Lyme disease.

Authors of the new study, which appears in the open access journal BioMed Central Biology, conducted their research on mouse models. The international team from France, Slovenia, and Poland found that DEET blocked the activity of an enzyme called acetylcholinesterase, which breaks down acetylcholine, a highly active neurotransmitter (chemical messenger) that is critical for optimal functioning of the central nervous system.

In a BBC News report, researcher Vincent Corbel said that “These findings question the safety of deet” and that they also “highlight the importance of a multidisciplinary approach to the development of safer insect repellents for use in public health.” Corbel and his team noted that more research is necessary to discover any potential neurotoxicity to humans.

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The EPA reports that about 33 percent of Americans are expected to use DEET each year. Currently about 39 different companies have registered approximately 140 lotions, sprays, liquids, and impregnated materials (e.g., wristbands) that contain DEET with the EPA.

In response to the results of this study, the EPA has maintained that DEET does not present a health concern if people use it as directed on product labels. Generally, consumers are urged to use only enough of the repellent to cover exposed skin or clothing and to never apply DEET to open or irritated skin. The EPA says it will consider the findings of the international study at its next review of DEET planned in 2012.

Despite reassurances from the EPA, individuals who are concerned about the possible toxic effects of DEET may want to consider insect repellents that do not contain DEET. Natural insect repellents are another option, including those made from plant oils such as citronella, lemongrass, peppermint, and cedarwood.


BBC News online 8/5/09
Corbel V et al. BMC Biology 2009; 7:47; doi:10.1186/1741-7007-7-47.
Environmental Protection Agency website