How to Safely Use Permethrin on Clothing

Hiking shoes and gear shown with a bottle of Insect Shield insect repellent permethrin spray

This insecticide can help prevent some mosquito and tick bites. But you must use it properly.

Excerpted content courtesy of Consumer Reports

When it comes to preventing bites from mosquitoes and ticks, remember: Summer isn't over yet, so it's important to remain vigilant and stay protected when you head outdoors. Insect Shield offers three solutions. In addition to our clothing with built-in insect protection, we offer permethrin spray that you can apply to clothing yourself, and our permethrin clothing treatment service: We add our patented permethrin treatment to clothes you send to us!

You may think first of insect repellents, such as products containing deet. Using an effective repellent is one of the best ways to keep biting bugs away. It’s also helpful to take steps that safeguard your yard against these pests.

But the Centers for Disease Control and Prevention also recommends another strategy on top of those two: treating your clothing with a pesticide called permethrin. (A repellent keeps bugs away; a pesticide kills them on contact.)
Permethrin-treated clothing, first developed by the military a few decades ago, has been available to consumers since 2003. And there are a few ways to use it. You can buy pretreated clothing from various manufacturers (especially those that specialize in outdoor gear). At least one company, Insect Shield, will treat your clothes with permethrin for you, if you mail them in. And you can do it yourself: Permethrin spray is available for consumers to buy and apply to their own clothing and gear.
“If it’s used correctly, it works really well,” says Thomas Mather, Ph.D., director of the University of Rhode Island’s Center for Vector-Borne Disease, of treating clothing with permethrin yourself. But the key, he says, is to use it correctly, which not everyone does.
Here, we’ll explain why permethrin-treated clothing might be an option you want to consider for protection against ticks and mosquitoes, how to make sure you get the best protection, and how to treat clothing with permethrin the right way.

How Well Does Permethrin Treated Clothing Work?

Permethrin is “very irritating to [the mosquitoes],” says Joe Conlon, a former Navy entomologist and technical adviser to the American Mosquito Control Association. “It’s like they landed on an electric grid.”
The permethrin-treated clothing also resulted in “knock downs,” meaning mosquitoes were incapacitated or killed after contact with the clothing. (Other research has found that knock downs might reduce biting rates in a specific geographical area.) The shirts we sprayed with deet didn’t cause any knock downs, however, because no bugs ever landed on them.
And what about ticks? Consumer Reports’ testing hasn’t evaluated how well permethrin-treated clothing works against ticks. But a recent study by researchers at the CDC found that a variety of different types of treated clothing was able to incapacitate several species of ticks or cause them to fall off the fabric. The researchers in that experiment didn’t use human subjects, however, so they couldn’t say whether the permethrin kept ticks from biting.
Other research has used human test subjects, however. For example, a 2014 study in North Carolina forest, park, and wildlife agency workers had the workers track the number of tick bites they received while using clothes professionally treated with permethrin. During the 2011 tick season (mid-March through September), workers who wore treated clothing reported fewer tick bites—0.24 bite for every 100 hours spent working—than those using untreated clothing, who averaged 1.37 bites during the same amount of time.
Manufacturers of permethrin spray for clothing note that because the spray is meant only for fabric and not for skin, for full protection people also need to use an insect repellent on their exposed skin. Consumer Reports’ experts agree.

How to Treat Clothing With Permethrin

The most important thing to remember when spraying your clothing with permethrin is that you must follow the label on the product. If you don’t follow the label, you could be violating federal law, Conlon says. (Because permethrin is a pesticide, the Environmental Protection Agency regulates its use.)
It’s also important to follow the instructions on the label to ensure you’re using the pesticide as safely as possible, says Michael Hansen, Ph.D., Consumer Reports' senior scientist. “It's an endocrine-disrupting compound," he says. That means “if it gets into your system, there can be effects on the hormonal system."
The CDC notes that permethrin and related chemical compounds can cause serious health problems in people exposed to high doses. “You don't want to be inhaling it or getting it directly on your skin," Hansen says.
If you follow the directions on the label, however, the dose of permethrin you receive by wearing treated clothing is considered safe, even for pregnant women. (Higher concentrations of permethrin are used in medications for treating both head lice and scabies.)

Permethrin Safety Tips

Spray only your clothing. We said it before, but it’s worth repeating: Permethrin spray is only for your clothes and gear. Don’t apply it to your skin. And when treating clothes, stick to outerwear: The Environmental Protection Agency says you shouldn’t treat underwear with permethrin.

Spray while the clothes are off your body. Hang them on hangers outside, and spray them down while they hang. Don’t apply permethrin to your clothes while you’re wearing them, and don’t apply permethrin indoors, where you could risk inhaling it.

Spray enough, but not too much. Mather says he often sees people making the mistake of giving their clothes a quick spritz of permethrin. But it takes a slightly heavier hand for full protection. Mather says you should spray enough for your clothes to become damp (they should look a little darker in color). You don’t need to drench them—to where they’ll drip if you wring them out—but they do need a thorough coat.

The product labels can help give you a good idea of how much to use. For example, the label on Sawyer’s permethrin aerosol spray says that a 9-ounce bottle will treat a shirt, a pair of pants, and a pair of socks.

Let the clothes dry completely. Before you wear them, they should be totally dry. That should take a few hours, depending on the humidity of the day.

Re-treat when necessary. Manufacturers of pretreated clothing say their products are still effective after many washes (L.L.Bean claims 70, for example). But the clothes you treat yourself need to be re-treated much more often. Sawyer says you need to re-treat after six washings, for example. Even clothes or gear you don’t wash need re-treating; Mather says he sprays his and his family’s shoes monthly.

Actually wear them. Mather says some people say they’re saving their permethrin-treated clothing for heavy-duty camping or hiking. But ticks don’t live just in the deep woods. If you live in an area where ticks are common, he recommends using protection even during casual activities, like taking your dog for a walk.

Consider treating other gear. Conlon says that camping gear like tents, backpacks, and hiking boots are also good candidates for treating with permethrin.

Wash treated clothing separately. Sawyer recommends hand washing or using the gentle cycle on your machine to best preserve the protection.

Only use permethrin approved for clothing. That will be indicated on the label.

You may be tempted to purchase permethrin pesticide (or related chemicals) meant for agricultural uses and dilute it down to a concentration of 0.52 percent, the industry standard for clothing. Not only is that illegal but it’s also risky, because you could make a mistake and end up with the wrong concentration. And there’s no guarantee it will work as well, Mather says, because the permethrin products meant for clothes are formulated with ingredients that help it stick to fabric. The agricultural products may not have those ingredients.

Don't rely on permethrin alone. Using permethrin-treated clothing is one useful step to take for preventing bites. But it's not the only one. Because permethrin goes only on clothes, if you rely on it alone, you still leave plenty of skin exposed and vulnerable to a bug's bite. To protect your exposed skin, use an effective insect repellent, such as one that contains 15 to 30 percent deet, 20 percent picaridin, or 30 percent oil of lemon eucalyptus. Make sure you apply it right, and remember you can use repellent on your clothing as well if you'd rather skip the permethrin.