Insect Repellent Study Reveals Widely Varied Protection Levels

In carefully controlled independent tests using mosquitoes and human subjects, insect repellents containing DEET provided complete protection from bites for the longest duration, according to an article in the July 4 edition of the New England Journal of Medicine.

Mark S. Fradin, M.D., and Jonathan F. Day, Ph.D., conducted the study at the University of Florida Medical Entomology Laboratory in Vero Beach. The researchers tested four consumer products containing DEET, seven botanical products incorporating other repellents, a recently introduced chemical repellent, a skin moisturizer commonly claimed to offer insect protection and three repellent wristbands.

"Only products containing DEET are dependable for long-lasting protection after a single application," Fradin and Day wrote, based on the test results.

"This rigorous new study confirms what experts have known for years -- that DEET is the most effective personal insect repellent available," said Susan Little, an industry spokesperson with the Consumer Specialty Products Association. "It also reinforces what other independent studies and our own industry tests have shown about DEET's effectiveness." "This is an especially valuable study, given the concerns of health professionals and the public about the continuing and rapid spread of West Nile virus and other mosquito-borne illnesses," Little said. "And, while this study focused on mosquitoes, previous research proved DEET's effectiveness against ticks, which carry Lyme disease and other tick-borne illnesses."

"Not only is DEET more effective than other repellents, it has been studied extensively by scientists and used reliably by Americans since 1957, Little says.

"When applied with common sense, DEET-based repellents can be expected to provide a safe as well as long-lasting repellent effect," Fradin and Day wrote.

A private-practice dermatologist and clinical associate professor of dermatology at the University of North Carolina-Chapel Hill, Fradin was often asked by patients what insect repellents to use. This prompted him to thoroughly review research published in peer-reviewed scientific and medical literature. In this assessment, which the Annals of Internal Medicine published in 1998 (see http://www.acponline.org), Fradin said, "Used by millions of people worldwide for 40 years, DEET has a remarkable safety profile."

A professor of medical entomology at the University of Florida, Day has studied repellents for many years. He urges parents to help prevent insect and tick bites by dressing their children in light-colored shirts with long sleeves and long pants, avoiding the peak times of day for mosquito activity - around dawn and dusk - and using personal insect repellents. "There are citronella-based, eucalyptus-based, DEET-based, soybean-oil based and IR3535-based repellents," Day said. "Without exception, the ones that work the best are the DEET-based repellents." He reports that DEET works by confusing mosquitoes and other biting pests' ability to hone in on the carbon dioxide that attracts them to humans and other mammals.

"The mosquitoes just sit down for about three hours rather thantrying to bite," he said. The U.S. Environmental Protection Agency carefully evaluates all DEET-based repellents before registering them for consumer use, noted Little. The EPA has determined that the use of currently registered products containing DEET, when label directions are followed, regardless of the concentration, will not pose unreasonable risks or adverse effects to humans.

"This is important because higher concentrations of DEET are needed when users are outdoors for extended periods or are in heavily infested areas where they encounter dense populations of biting insects and ticks," Little said.

For additional information about repellents and protection from insect and tick bites, go to http://www.deetonline.org.