Treating your clothes with permethrin is one of the most effective ways to protect yourself from ticks, mosquitoes, and other biting insects. The standard consumer concentration is 0.5%, which is what you’ll find in ready-to-use sprays like Sawyer’s. You have two main methods: spraying or soaking. Both work, but they differ in how evenly the permethrin bonds to the fabric, how long the protection lasts, and how much effort is involved.
How Permethrin Protects You
Permethrin isn’t a repellent in the way DEET is. It’s a neurotoxin for insects. When a tick or mosquito lands on treated fabric, permethrin disrupts the sodium channels in its nervous system, causing paralysis and death. Insects don’t need to bite you for the chemical to work. Contact with the treated surface is enough. This makes it especially useful for ticks, which crawl across clothing before finding skin.
The Spray Method
Spraying is the faster and more common approach. Here’s how to do it well:
- Work outdoors. Choose a well-ventilated area out of the wind. Lay the garment flat on a surface you don’t mind getting overspray on, like a tarp or cardboard.
- Hold the can 6 to 8 inches away. Spray in slow, even passes across the entire surface of the garment. You want full, even coverage without soaking the fabric to the point it’s dripping.
- Flip and repeat. Treat both sides of the garment, paying attention to cuffs, collars, and seams where ticks commonly crawl.
- Let it dry completely. Hang the treated clothing and allow it to air dry before wearing. This typically takes two to four hours depending on humidity.
One standard bottle of 0.5% permethrin spray (24 oz) can treat several garments. Focus on the items that matter most: pants, socks, shoes, and shirt sleeves. You don’t need to treat undergarments or anything that won’t be exposed to the outdoors.
The Soak Method
Soaking produces more uniform coverage because the permethrin saturates the entire fabric rather than just the outer surface. This method is worth the extra effort if you’re preparing gear for an extended trip or treating multiple items at once.
You can use a pre-mixed 0.5% permethrin solution, which eliminates the need to dilute concentrated product. Sawyer recommends about 3 ounces of 0.5% solution per garment. Pour enough into a sealable plastic bag or small basin to fully submerge the item, then let it soak for a few hours. Some commercial kits include a zip-top bag and a small bottle of permethrin concentrate that you mix with a half liter of water before adding your garment.
After soaking, remove the garment and hang it to dry completely. Do not rinse it. The goal is to let the permethrin bind to the fibers as the water evaporates.
Which Fabrics Work Best
Permethrin bonds to most common outdoor fabrics, including cotton, polyester, and nylon. Research shows that different fiber types absorb and retain insecticides at different rates. Cotton tends to hold permethrin well, while synthetic blends may release it slightly faster with washing.
For waterproof or water-resistant shells with DWR coatings, spray application is safer than soaking since the coating is designed to repel liquids. Permethrin won’t damage most technical fabrics, but it’s worth testing a small, inconspicuous area first if you’re treating expensive gear. Avoid treating silk or delicate fabrics where the solvent carriers in the spray could leave marks.
How Long the Treatment Lasts
This is where the method and product type matter significantly. DIY spray and soak treatments lose potency faster than factory-treated garments because the permethrin sits on the fiber surface rather than being locked in with a polymer coating.
Research on DIY-impregnated clothing shows a roughly 50% decline in permethrin concentration after just two to four washes. After 16 washes, concentrations dropped by 50 to 90% compared to freshly treated clothing. That said, the treated fabric still showed meaningful insecticidal effects even at reduced concentrations. For practical purposes, plan to re-treat spray-applied clothing every five to six washes, or roughly every few weeks if you’re wearing and laundering the garments regularly.
Factory-treated clothing uses a polymer bonding process that performs far better. One study found only a 10% decline in permethrin concentration after 10 washes, and some factory-treated uniforms maintained effective levels past 70 washes. If you want long-lasting protection without re-treating, factory options from brands like Insect Shield are worth considering.
Washing Tips to Extend Protection
Wash treated clothing separately from untreated items. Use cold or warm water rather than hot, and avoid bleach. Tumble drying on medium heat is fine. Research on military uniforms found that wearing alone caused minimal loss of permethrin (about 5% after 132 hours of wear), while machine washing was the primary driver of decline.
Safety for You
Permethrin on dried clothing poses very little risk to humans. Your skin absorbs almost none of it. A study of outdoor workers wearing permethrin-treated uniforms daily for three months found that their absorbed dose averaged less than 4 micrograms per kilogram of body weight per day. That’s more than 60 times lower than the European acceptable daily intake and more than 60 times below the EPA’s chronic reference dose.
The EPA has evaluated multiple exposure scenarios for permethrin-treated clothing, including toddlers wearing and mouthing the fabric. All scenarios fell below their level of concern. There is no evidence of reproductive or developmental effects from wearing treated clothing.
The one moment to be cautious is during application. Wet permethrin can irritate skin and eyes, and inhaling the spray is not ideal. Wear gloves when handling freshly treated clothing, apply it outdoors, and wash your hands after. Once the fabric is completely dry, the permethrin is bound to the fibers and poses negligible risk.
Permethrin Is Toxic to Cats
This is the one serious safety concern. Cats are extremely sensitive to permethrin because they lack the liver enzymes needed to break it down. In a review of 286 cases of cats exposed to permethrin spot-on products, 96.9% developed symptoms. Convulsions and tremors were common, lasting an average of 33 to 39 hours, and 10.5% of exposed cats died.
The concentration on treated clothing is far lower than a spot-on product, but wet permethrin is the real danger. Keep cats away from freshly sprayed garments and from any area where you’ve applied the solution. Once clothing is fully dry, the risk drops dramatically, but it’s still smart to store treated gear somewhere your cat doesn’t sleep or groom. Dogs, by contrast, tolerate permethrin well and are even prescribed permethrin-based flea treatments.
Storing Treated Clothing
Permethrin breaks down when exposed to sunlight and UV radiation. Store treated garments in a dark closet, drawer, or sealed bag when not in use. If you’re packing for a trip, keeping treated clothes in a zip-top bag also prevents the permethrin from transferring to untreated items. There’s no need to refrigerate treated clothing. Room temperature storage out of direct light will preserve the treatment between uses.