Hikers, campers, landscapers and others who play or work outdoors might want to consider buying some new clothes, if they don’t already own them. According to a story aired on National Public Radio’s Morning Edition, a new study has confirmed that clothing treated with permethrin, a natural insecticide derived from chrysanthemums, works well to kill the arthropods whose bites spread Lyme disease, Rocky Mountain Spotted Fever and others.
Of course, this anti-tick strategy is nothing new. In the 1980s, the U.S. military conducted studies that showed that clothing impregnated with permethrin was effective in preventing tick and insect bites and began purchasing uniforms treated with the stuff. Any ticks that come into contact with treated clothing rapidly become incapacitated and unable to bite.
Researchers at the Centers for Disease Control and Prevention conducted the most recent study, published in May in the Journal of Medical Entomology. They purchased 10 different types of permethrin-treated clothing, including T-shirts, socks and pants from a company called Insect Shield, one of the makers of such gear.
Different species of ticks were put on a bit of treated cloth the size of a playing card. "We wanted to see how long [the ticks would] have to be in contact with the clothing to be incapacitated and die," says Lars Eisen, a research entomologist for the CDC and one of the study's authors.
The ticks quickly became irritated after exposure to the pesticide. "They essentially start flipping backwards and start rolling off the treated clothing," says Eisen.
One of the species tested was the black-legged tick, also known as the deer tick, known for transmitting the bacteria that causes Lyme disease.
It took less than a minute for black-legged tick nymphs (young ticks no bigger than a poppy seed) to receive a fatal dose of permethrin after coming in contact with a piece of treated clothing, Eisen says.
Even though the ticks don't die instantly, the permethrin quickly incapacitates them so that they're unable to bite.
"There are several studies that provide pretty compelling evidence that wearing permethrin-treated clothing has the potential to reduce tick bites," says Neeta Connally, a medical entomologist who oversees the Tickborne Disease Prevention Lab at Western Connecticut State University.
Still, only a few people take advantage of permethrin-treated clothing. One study conducted in Connecticut and published in 2009 showed that less than 1 percent of its participants said that they ever wore treated clothing.
The reason may have been unearthed by a more recent survey, which found that many respondents were uncertain about the effectiveness and safety of treated clothing.
They needn’t be; permethrin has been registered with the Environmental Protection Agency since 1979, and the agency periodically reevaluates it.
"I absolutely wear permethrin-treated clothing," says Connally, who has no financial ties to any of the makers of permethrin or clothing treated with it. Many researchers in her lab wear permethrin-treated overalls while doing tick research.
"When I think of the potentially serious illnesses that my family members or I could get from a single tick bite, I feel very comfortable wearing treated clothing," she says.