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Mosquitoes Less Repelled by DEET After First Exposure

A powerful weapon in the battle against mosquitoes has a fatal flaw. The insects are able to ignore the widely-used repellent DEET just a few hours after being exposed to it.

In the journal PLOS ONE, researchers from the London School of Hygiene and Tropical Medicine report that DEET appears to be effective at keeping the insect away for up to three hours. In their study, they used Aedes aegypti mosquitoes, which can transmit dengue fever. They found that a brief exposure to DEET was enough to make some of the insects less sensitive to the repellent, so they were not put off by DEET-treated skin when they encountered it the next time.

Lead author James Logan compares the phenomenon to humans becoming accustomed to an odor, to the point when they no longer smell it. He stresses that the research does not mean people should stop using DEET and other repellents, especially in areas at high risk of mosquito- or fly-borne disease. Instead, he says, it suggests a new direction for 'chemical warfare' against the biting insects.