Insect Repellent Safety Information

Hiking - Masterfile

If you spend time in tick-infested areas, using permethrin on clothing may be a good investment. In a recent small study from the University of North Carolina at Chapel Hill, outdoor workers who wore uniforms treated with permethrin (a synthetic repellent/insecticide similar to a natural chemical in chrysanthemums) had 93 percent fewer tick attachments, overall, than those using other repellents and prevention methods. Permethrin combats mosquitoes, black flies, ticks and chiggers, ants and other critters.

The Department of Defense has been using permethrin-treated uniforms for over 20 years with no adverse effects reported. Though the chemical has been classified as a possible carcinogen, the evidence comes from animals fed high doses, while people are exposed to much lower amounts and do not ingest permethrin.

According to the CDC and the National Academy of Sciences, treated clothes pose little health risk to people (little even gets on your skin, and it's broken down quickly). There has not been adequate research on its effects on human fetuses, however, so pregnant women should avoid it. And it's still a good idea for everyone to minimize exposure to all insecticides, synthetic or natural. Save permethrin-treated clothes for when you are in very buggy areas or if you are particularly prone to stings. Don't wear them as your everyday clothes or indoors.

Several retailers market clothes—shorts, shirts, hiking pants, socks, hats—treated with Insect Shield technology (which was used in the recent study). You can find them at some sporting-goods and camping stores and on the Internet. A cheaper option is to buy permethrin sprays and concentrates to treat your own clothes (follow directions carefully). Once dry, permethrin leaves no scent. It should not be used on skin, since that deactivates it.

Keep in mind: You still need to apply topical insect repellents to exposed skin for optimal protection. DEET remains the gold standard; picaridin has also been deemed effective; and oil of lemon eucalyptus is modestly effective. And remember, clothing, treated or not, is still your best defense against insects. Wear long sleeves and long pants (tucked into your socks or boots) when out in the woods or tall grass.

Source: Originally published in The University of California, Berkeley Wellness Letter (August 2011)

Publication Review By: the Editorial Staff at

Published: 13 Jul 2011

Last Modified: 21 Oct 2014