From Consumer Reports:
Shirts, pants, hats, and other clothing treated with
the insecticide known as permethrin have been touted for 15 years as a way to prevent the tick bites that can lead to Lyme disease, Rocky Mountain spotted fever, and more. But research hadn’t proved that permethrin-treated clothing items are actually effective tick-stoppers.
Tick-borne illnesses, especially Lyme disease, are on the rise and occurring in an increasingly wide area, according to a
recent report from the Centers for Disease Control and Prevention, making it more important than ever to protect against tick bites.
Now,
a new study by CDC researchers has found that just a minute or two of contact with permethrin-treated clothing caused ticks to become incapacitated or fall off fabric.
The research examined a variety of permethrin-treated clothing types and fabrics. It revealed that the items can be toxic to several species of ticks and at different stages in their life cycles, potentially keeping them from getting beneath clothing and staying next to skin long enough to bite.
While the CDC research sounds promising, it’s still unclear whether the permethrin-embedded apparel actually prevents bites, says James Dickerson, Ph.D., Consumer Reports’ chief scientific officer.
"The CDC’s study did not test any items while they were being worn, so it doesn’t show conclusively how well the clothes might keep ticks from biting you," Dickerson says.
Consumer Reports has tested the effectiveness of permethrin-treated clothing but only for its ability to stop the bites of mosquitoes, not ticks.
In our tests, permethrin-treated shirts from L.L.Bean and ExOfficio treated with 0.52 percent permethrin—the industry standard—did kill or incapacitate mosquitoes. But in some cases the mosquitoes were still able to bite wearers. (For more on this testing,
see our report.)
Permethrin is sometimes referred to as a repellent—which keeps bugs from landing on you—but it functions as an insecticide, which means it poisons insects.
To determine whether permethrin-infused clothing actually stops tick bites, a larger study is needed in which people wear regular or treated clothing and go about their normal outdoor activities, says Eisen of the CDC. “We do not have that study yet,” he notes.
Still, "we know that permethrin-treated clothing is toxic to ticks," he says. "So we are assuming that if you are adequately covered by permethrin-treated clothing, there’s no reason it should not be protective.”
The Environmental Protection Agency says that the amount of permethrin allowed in treated clothing and other consumer products is safe. (It’s also in some insect sprays, which are meant to be used on clothing before you put it on, as well as in products like some head lice treatments.)
It is not recommended, however, that permethrin be sprayed directly on skin, and the EPA considers it a likely human carcinogen when ingested.
The CDC includes permethrin-treated clothing in its recommendations for
preventing tick bites along with other measures, like those below.
Consumer Reports' experts are more cautious. Dickerson says that while there’s likely little harm in wearing permethrin-treated clothing, using a bug repellent, rather than an insecticide, should be your first line of defense.
“Repellent is the best way to ensure that bugs don’t have an opportunity to bite you,” he says.
Consumer Reports tests insect repellents each year for their effectiveness against mosquitoes. Our experts say that the repellents that work best against mosquitoes are also the ones that are likely to be most effective against ticks, too.