OFF! Skintastic with a 6.65 percent DEET concentration offered complete protection for an average of almost two hours. Bite Blocker for Kids, in which the active ingredient is 2 percent soybean oil, lasted an hour and a half on average, he said.

Various Skin-So-Soft products, including those containing either the chemical IR3535 or plant based citronella protected, on average, far less than 20 minutes. Recently introduced oil of eucalyptus repellents Fite Bite and Repel lasted an average of two hours.

"If you are outside at a barbeque in the United States, this variability probably won't make much difference," Fradin said. "But if you are looking for prolonged protection that's reliable, especially in tropical and subtropical countries where mosquito-borne diseases are endemic, then your best bet would be to choose products containing DEET."

Worldwide, mosquitoes transmit diseases to 700 million people a year, he said. Malaria alone still kills up to 3 million people annually. Even in the United States, various forms of mosquito-borne encephalitis show up from time to time, and West Nile virus, which has been detected to date in 27 states, killed seven people in the New York City area two years ago.

DEET's toxicity gets a lot of news media attention every year, but the UNC dermatologist said concerns about that appear to be grossly exaggerated.

The "very safe" product has been on the market for some 45 years, and fewer than 50 cases of significant toxicity have been reported in the medical literature.

"In many of those cases, there was excessive, very inappropriate use of a DEET product in which someone was applying a high-strength formulation and covering large areas of skin for many days in a row," Fradin said.

Estimates are that DEET-based products have been used between 5 billion
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Contact: David Williamson
david_williamson@unc.edu
919-962-8596
University of North Carolina at Chapel Hill
3-Jul-2002