Organic Consumers Association

OCA Warns About Using DEET Insect Repellent

Columbus Dispatch (Ohio)

August 8, 2003



The best insect repellent can get under your skin.

DEET is widely embraced as the most effective insect repellent at a time of growing fear of mosquitoes and ticks. DEET (N, N-diethyl-3-methylbenzamide) masks the chemical signals that insects use to find their victims.

And it is partially absorbed into human skin.

Opinions vary on the safety of DEET. Many researchers urge its careful use to prevent insect-borne diseases; others, including those in the organic community, believe the chemical should be avoided in most cases.

Most researchers agree with the U.S. Environmental Protection Agency that exposure to DEET should be brief.

Mosquitoes can carry encephalitis and the West Nile virus; the black-legged tick, often called a deer tick and not native to Ohio, can spread Lyme disease.

The Centers for Disease Control and Prevention recommends use of insect repellent when outside for "even a short time." The agency Web site shows a man spraying his clothing with a DEET product to discourage the spread of West Nile virus.

An article a year ago in the New England Journal of Medicine says DEET "has a remarkable safety profile after 40 years of use and nearly 8 billion human applications." A 1998 article in the Annals of Internal Medicine calls DEET "the most effective, and best studied, insect repellent."

The organic community is not so sure.

"It's a scary chemical, and it's definitely to be used only as a last resort, if at all, to protect yourself from insect bites," said Ronnie Cummins, national director of the Organic Consumers Association, based in Minnesota.

"I think this issue of West Nile virus has been overblown in the press," he said. "People are being encouraged to put stuff like DEET on their skin, and scientists know that can be harmful.

"The skin is like a million mouths. Whatever you put on your skin is like eating it . . . and going straight into your bloodstream."

Summarizing a Duke University study, the National Coalition Against the Misuse of Pesticides said, "With heavy exposure to DEET . . . humans may experience memory loss, headache, weakness, fatigue, muscle and joint pain, tremors and shortness of breath." The stuff is also linked to skin and eye irritations.

DEET was developed by the Army in 1946, was made available to the public in 1957 and is included in more than 200 products, the EPA said. About a third of the U.S. population uses DEET each year.

The EPA evaluated DEET in 1998 and decided "As long as consumers follow label directions and take proper precautions, insect repellents containing DEET do not present a health concern."

The EPA then required more prominent display of label directions for what it considers a slightly toxic substance.

In general, the higher the concentration, the longer the protection and the greater the risk. The American Mosquito Control Association says repellents should be used sparingly and that concentrations of more than 30 percent DEET should be avoided.

An analysis of 34 insect repellents by found 13 with DEET, ranging in strength from 7 percent (Cutter All Family) to 100 percent (Sawyer Maxi DEET and 10-Hour Insect Repellent).

About 48 percent of DEET is absorbed through the skin within six hours, according to the coalition against pesticide misuse.

Studies of U.S. Army soldiers, lumber workers and Everglades National Park employees, who were exposed over time to DEET solutions of up to 75 percent, showed various skin and mucous-membrane ailments.

"It's not an ideal, perfectly safe drug," said Dr. Marcel Casavant, medical director of the Central Ohio Poison Center headquartered at Children's Hospital.

"There are definitely side effects," he said. "But it turns out the side effects, although dramatic, are very, very uncommon."

Neurological damage, including rare seizures, have been reported, but those are mostly "because the material hasn't been applied properly, hasn't been washed off or there was re-dosing too soon," Casavant said.

He warned against prolonged use and "multiple, repeated" doses.

"We used to say DEET was fine for grown-ups and that low concentrations or a less-toxic alternative were preferred for children," he said.

The recommendation of a lower dose for children has been dropped, he said, because of the increased threat of insect-borne disease and because studies show a 10 percent dose "isn't that much safer" than a 30 percent dose.

Casavant is confident enough in the product's safety to have used some this year during a walk in the woods.

"I don't think you have to use chemicals," he said. People can stay indoors, particularly at dawn and dusk, and they can cover up with long-sleeve shirts and long-legged pants.

"You can limit your exposure."

Box Story:Do's and don'ts
* Read directions and precautions.
* Don't apply over wounds or skin irritations.
* Don't apply to hands or near the eyes or mouths of young children.
* Don't let young children apply the product.
* Use just enough to cover exposed skin and clothing.
* Don't use under clothing.
* Don't apply too much.
* Wash treated skin after returning indoors.
* Wash treated clothing.
* Don't spray in enclosed areas.
* Don't spray on face.
Source: U.S. Environmental Protection Agency
Natural options
Plants whose oils are reported to repel insects include allspice, basil, cedar, cinnamon, citronella, garlic, geranium, lavender, neem, peppermint, pine, rosemary, thyme, and verbena. Most plant-derived repellants have not been thoroughly studied. In tests, plant-based repellents show shorter periods of protection, usually less than two hours.

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