New mosquito repellents without DEET are very promising

Entomologists and research scientists have found several new mosquito repellents that appear to work more than three times as long as DEET. DEET — or N,N-diethyl-m-toluamide — has been used for 50 years and is still the gold standard. But new repellents are always needed because the threat from mosquito-borne diseases like malaria, yellow fever, West Nile virus and Rift Valley fever is growing. Chemists at the University of Florida and the United States Department of Agriculture screened many acylpiperidines, which are related to the active ingredient in pepper. Their study was published online Monday in The Proceedings of the National Academy of Sciences.

In tests on humans, they found that some acylpiperidines could repel mosquitoes for up to 73 days, while DEET typically lasted only 17 days. However, the tests did not replicate typical exposures. Volunteers wore thick gloves with holes, over which were taped pieces of muslin soaked in repellent, and their arms were thrust into cages of mosquitoes for only one minute. “Failure to repel” was recorded on the first day that five mosquitoes bit through the cloth. Tests of commercial repellents in 2002 done with bare skin found that the most effective were those that contained the most DEET — and they lasted only about five hours.

Obviously, we need further tests to see whether the acylpiperidines irritate skin, evaporate, dissolve in sweat or fail in ways that other repellents do. This research was going on for a long time now. One of entomologists from North Carolina State University has developed biological means to avoid DEET in his repellents, but still waiting on the patent.

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