DEET repels bugs, worries consumers

Put simply, DEET makes many consumers nervous.

Considering that billions of people have used the insect repellent safely, the case reports of related illness or fatalities are extremely rare. But neither the reassurances nor the studies on DEET’s safety have been conclusive enough to allay fears.

Donald Roberts, a retired professor of tropical public health at the Uniformed Services University of the Health Sciences in Bethesda, Md., says the health risks of DEET, or N,N-Diethyl-meta-toluamide, have been overblown: “I believe DEET is basically a safe compound and can be used and should be used to give people protection from biting insects.”

The Environmental Protection Agency would seem to agree.

After performing a comprehensive safety re-assessment of the compound in 1998, the EPA concluded: “As long as consumers follow label directions and take proper precautions, insect repellents containing DEET do not present a health concern. Human exposure is expected to be brief, and long-term exposure is not expected. Based on extensive toxicity testing, the agency believes that the normal use of DEET does not present a health concern to the general population.”

In a 2001 study in the American Journal of Tropical Medicine and Hygiene, researchers investigated the effects of DEET use in the second and third trimesters in 900 pregnant women and their babies and found that DEET was present in 8% of cord blood samples from the offspring, demonstrating that the chemical can cross the placenta.

But no adverse effects were found in growth and development of the children at birth or one year, and the authors concluded that the repellent is safe to use during the second and third trimesters of pregnancy.

The Agency for Toxic Substances and Disease Registry, part of the U.S. Department of Health and Human Services, offers a comprehensive list of studies and case reports on the health effects of DEET. Overall, it concludes: “In the more than 45 years that DEET has been used in the U.S., reports of adverse effects in humans associated with the dermal application of DEET have been relatively rare, given the billions of applications of the repellent.”

The few cases

“Relatively rare” means that, in a few cases, fatalities have resulted following direct ingestion or skin application of the insect repellent and that its use has been linked to reproductive and developmental effects in a handful of cases.

From 1961 to 2002, eight deaths from DEET exposure were reported in the medical literature, including three from deliberate ingestion, two from skin exposure and three in female children ages 17 months, 5 years and 6 years, respectively. In the last three cases, “heavy,” “frequent” or “nightly” applications of DEET were reported.

The 6-year-old had a potentially lethal congenital disease that may have played a role in her death, according to the study. The two people who died after skin exposure to DEET were a 26-year-old man and a 34-year-old woman, according to a 2002 study from the International Journal of Toxicology. That research analyzed 20,764 DEET exposures reported to poison control centers from 1993 to 1997.

In a 1992 study, DEET was implicated in a case of possible reproductive effects in a 34-year-old pregnant woman who applied a 25% formulation daily during her pregnancy. Her child was born with numerous developmental abnormalities, and the authors concluded that DEET may have played a role.

There are no age restrictions for the use of DEET in the U.S., though the American Academy of Pediatrics recommends that the compound not be used on infants less than 2 months old.

In the European Union, the repellent is approved only for use up to 15% strength — and not approved at all for use in children younger than 2 years. EU regulations also require that DEET be used only in limited amounts on small skin surfaces in children younger than 12. (DEET is regularly sold in formulations up to 30% strength and sometimes much higher in products in the U.S. The EPA approves its use on human skin up to 100% concentration.)

The Centers for Disease Control and Prevention website says: “Parents should choose the type and concentration of repellent to be used by taking into account the amount of time that a child will be outdoors, exposure to mosquitoes, and the risk of mosquito-transmitted disease in the area.” The EPA says that DEET should not be used under clothing and should be washed off with soap and water following its use.

Weighing the fears

Many experts believe that DEET has been proved to be safe, given the millions and even billions of users over the years.

Fears of DEET have led many people to resort to less effective alternatives, Roberts says. And he points out that insects are much more than just pests — they transmit disease and sometimes cause allergic reactions and itching that can lead to serious infection.

Scott Carroll, an evolutionary biologist at UC Davis and director of Carroll-Loye Biological Research Consulting, an independent company that does extensive testing on insect repellents, says that, compared with other products, such as ammonia-based household cleaners, DEET is relatively safe. Still, he acknowledges, “It causes anxiety, and I understand that.”

And then there’s the growing demand for green, non-toxic products in everything from household cleaners to cosmetics.

There are many people who have great concern about some of the chemicals in personal care products, and “those people will not buy DEET — they’re not going to put it on their children, no matter what,” says Dennis Tracz, founder of 141 Repellent, a Lexington, Va.-based company that has an exclusive license to develop an all-natural pine-oil derivative that is patented by the U.S. Department of Agriculture for use as an insect repellent.

Experts agree that, above all, DEET suffers from a perception problem.

But even Roberts recognizes that there is a great need for more effective options and alternatives, both for skin application and for spatial repellents to control malaria in the developing world. Some people have sensitivities to the compound, while others will just opt not to use it because of safety concerns.

“We just need a greater array of chemicals that people can consider and use,” he says.

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