Permethrin is a pesticide in the pyrethroid class, and research suggests that it may have some potential health risks.
A 2019 study that followed more than 2,000 adults over 14 years found that people with higher exposure to pyrethroids had an increased risk of dying from heart disease. (The study involved a small number of people, however, and couldn’t establish whether pyrethroids caused the deaths or another factor was to blame.)
As with many other pesticides, permethrin has also been implicated as a possible endocrine disruptor, says CR senior scientist Michael Hansen, PhD. Endocrine disruptors mimic or block the activity of your hormones, which can have effects all throughout the body and brain.
Research suggests that permethrin can be found in the blood and urine of workers who wear treated clothing, which means it can be absorbed from clothes into the body. In one 2019 study, the levels of permethrin found in the urine of workers was well below both Environmental Protection Agency and World Health Organization limits for safe exposure to the chemical.
But endocrine-disrupting chemicals have the potential to cause harm at much lower doses than the legal limits, Hansen says. Young children and people who are pregnant may be most at risk from endocrine disruptors, so for people in these groups, thinking carefully about minimizing exposure (for instance, by using treated clothing infrequently or only in the highest-risk situations) is wise.
Ultimately, you’ll need to weigh the possible health risks of permethrin against the risk of contracting a tick-borne disease, many of which can have serious, long-lasting health consequences.
If you opt to treat your clothes yourself, additional safety measures are needed. First, make sure you are using spray formulated specifically for clothing; do not buy or use agricultural-grade permethrin, even if you dilute it.
Second, never spray when you are wearing the clothing you want to treat; clothing must be sprayed and then allowed to dry completely before you wear it. Permethrin should also never be sprayed around cats, for whom it is highly toxic. (See these tips on using permethrin safely.)
Permethrin is not your only option for protection. Public health experts say simple adjustments can make a big difference, such as wearing light-colored long pants and sleeves when you’re out in tick habitat, tucking in your shirt, pulling your socks up over your pants, and—when you return home—performing tick checks and taking a shower.
You can also consider insect repellents that contain deet, picaridin, and oil of lemon eucalyptus, all of which are registered by the EPA for protection against ticks.
