CHAPEL HILL In a new comparative study of insect repellents containing the chemical commonly known as DEET and plant-based repellents, products with DEET showed by far the greatest effectiveness in preventing mosquito bites, medical researchers say.
The study, appearing in the July 4 New England Journal of Medicine, found all products tested that did not contain DEET to be significantly less effective. Authors are Drs. Mark S. Fradin, a Chapel Hill, N.C., dermatologist and adjunct faculty member at the University of North Carolina at Chapel Hill; and John F. Day, professor of medical entomology at the University of Florida.
"We took 16 representative DEET and non-DEET products that were readily available to consumers as insect repellents and tested them carefully, repeatedly and in a way that eliminated as many variables as we could," said Fradin, clinical associate professor of dermatology at the UNC School of Medicine. "We controlled how many mosquitoes we had, their ages, how well-fed they were, what the temperature and humidity were, the levels of light and darkness and so on."
After volunteers applied various repellents to their skin according to package instructions, they placed their forearms in mosquito cages until they suffered their first bite, he said. Researchers recorded and analyzed the times that elapsed between arm insertion and the first failure of each repellent.
"We selected the time of first bite as a very stringent criterion for failure because the primary concern here is not nuisance bites but the possibility that diseases caused by mosquitoes could potentially be transmitted by a single bite," Fradin said.
Results varied widely, he said. DEET-based products fared best, depending on their concentrations. Wristbands impregnated with the chemical, however, offered no protection from mosquito bites.
OFF! Deep Woods, with 23.8 percent DEET, provided complete protection for an average of five
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Contact: David Williamson
david_williamson@unc.edu
919-962-8596
University of North Carolina at Chapel Hill
3-Jul-2002