How to wash permethrin-treated clothing (without washing it out)
Separate load or not, hot or cold, dryer or line: what the labels say, what the lab tests found, and one piece of laundry advice that doesn't hold up, including on this site until now.
Wash treated clothes separately from other laundry, as the labels and EPA say, and only when they need it: every wash costs some treatment. Water temperature makes no proven difference. The dryer is fine, including the high-heat cycle CDC recommends for killing ticks. Never dry-clean treated clothing, and skip hot ironing. Re-treat DIY-sprayed clothes after 6 washes or 6 weeks; don't re-treat factory-treated clothing with another permethrin product.
Laundry is where permethrin treatment quietly dies. The spray itself is easy (here's how to apply it); the questions start the first time the treated hiking pants hit the hamper. Can they go in with everything else? Will hot water wash it out? Does the dryer cook it off? We went through the product labels, the EPA guidance and the published wash studies, from the US Army's uniform research to two-year field trials, and the answers are mostly simpler than the forum threads suggest.
The care label we wish came sewn in
Separate load or not?
Follow the label: separate. Insect Shield's EPA-accepted label says to wash treated garments separately from other clothing, and EPA's own explanation is practical rather than alarming: small amounts of permethrin can come off in the wash, and the instruction keeps untreated items like underwear free of it. The National Pesticide Information Center gives the same advice. The US Army, which has washed more permethrin uniforms than anyone, says only very tiny amounts transfer to other garments, and still tells soldiers to follow the label.
You'll find brand blogs saying mixed loads are fine. Maybe they are, but the label is the legally binding instruction, and keeping the hiking clothes in their own load costs you nothing. It's also the easiest way to keep treated socks away from the baby's laundry.
Hot or cold: a myth we used to repeat
Earlier versions of our permethrin pages said hot water and heavy detergent strip the treatment fast, so wash cold. When we went looking for the evidence, we couldn't find a single study comparing wash temperatures. The washes in the published studies were cool or warm, and the losses were large either way. We've corrected those pages.
What the evidence does support: the number of washes matters far more than their temperature, and in the washer, agitation and detergent cause most of the loss. Sawyer itself recommends hand washing or gentle cycles and air drying for the longest life. And there's a reason to sometimes want hot water anyway: CDC notes that cold and medium-temperature water will not kill ticks clinging to clothes after a hike, while hot water will. The cleaner fix is the dryer. Ten minutes on high heat kills ticks on dry clothes, and Sawyer says the dryer costs far less treatment than the washer does.
How long treatment really lasts
The labels give you the ratings. Independent testing gives you the reality, and for factory-treated clothing the two don't match.
| Treatment | Rated for | What independent tests found |
|---|---|---|
| DIY spray (Sawyer and similar) | 6 washes or 6 weeks, whichever comes first | Matches the US military's own guidance for aerosol treatment: re-apply after 6 weeks or 6 launderings. |
| Factory-treated clothing (Insect Shield) | Up to 70 washes on the apparel label (25 for some gear) | Permethrin down 28% after 5 washes and about 82% after 30 (Banks et al., 2015); down 63–70% after 15 washes (Richards et al., 2018); down 50–90% after 16 cycles of wear and washing (a 2019 study with CDC co-authors). A two-year field trial of outdoor workers measured protection against tick bites of 82% in year one and 34% in year two. |
| Military uniforms (factory-treated) | The life of the uniform, about 50 launderings | The Army reports 99–100% bite protection up to 50 launderings for its factory-treated combat uniform, which uses its own industrial process. |
Less permethrin doesn't instantly mean no protection; in the 2015 lab study, it took about 33 machine washes to lose half of the treatment's insecticidal effect (measured against mosquitoes). But the honest planning number for factory-treated clothing is a season or two of strong protection, not the life of the garment. And in a 2022 study of treated work clothing, a third of participants' pants had no measurable permethrin left after a year of wear. Our DIY vs pre-treated comparison runs the cost math with these numbers in mind.
When and how to re-treat
- DIY-sprayed clothes: re-treat after 6 washes or 6 weeks, whichever comes first (Sawyer). One home-spray label adds two limits worth borrowing: no more than once every two weeks, and launder at least once before re-treating.
- Factory-treated clothes: don't. Insect Shield's label says not to re-treat with other permethrin products, and the Army says the same for its uniforms.
- Re-treating is the same job as the first treatment: outdoors, to slightly damp, both sides, dried completely. The six steps are here.
Two places treated clothes shouldn't go
Streams and lakes. Permethrin is highly toxic to fish and other aquatic animals, according to the National Pesticide Information Center. On a backpacking trip, wash treated clothing in a container and dump the water well away from any stream, lake or pond.
The dry cleaner. Dry cleaning removes permethrin from the fabric. A treated jacket that needs professional cleaning will need re-treating afterwards.
Cats: permethrin is toxic to cats while wet. Once treated clothing is completely dry, Sawyer and an ASPCA toxicologist both say it's safe around them. Nobody has studied damp, freshly washed treated laundry, so the cautious move is to dry it where the cat can't nap on it. Full detail: permethrin and cats →
Need a bottle for the next re-treat? We use 0.5% permethrin fabric spray, the same concentration Sawyer and Ranger Ready both sell: check the price on Amazon.
Frequently asked
Can you wash permethrin-treated clothes with other clothes?
The labels say no: wash permethrin-treated clothing separately. EPA explains that small amounts of permethrin can come off in the wash, and the instruction keeps untreated items such as underwear free of it. Some brands say mixed loads are fine, but the label on the product is the binding instruction, and a separate load costs nothing.
Does washing remove permethrin?
Gradually. Each wash removes some treatment, mostly through agitation and detergent; Sawyer says the dryer causes far less loss than the washer. A DIY spray is rated for about 6 washes or 6 weeks. Factory-treated clothing is rated for up to 70 washes, but independent lab tests found permethrin levels down by half or more within roughly 15 to 30 washes.
Can you put permethrin-treated clothes in the dryer?
Yes. Sawyer says loss in the dryer is limited compared with the washer, and the dryer is useful: CDC recommends tumbling dry clothes on high heat for 10 minutes after time outdoors to kill any ticks on them. What to avoid is dry cleaning, which removes permethrin, and hot ironing, which removed most of it in a lab study.
Does hot water wash out permethrin?
There's no good evidence that it does. We could not find a study comparing wash temperatures; the losses measured in cool and warm washes were large either way. Washing frequency and agitation matter more than temperature. CDC notes the opposite consideration for ticks: cold and medium-temperature water will not kill them, hot water will.
How many washes does Insect Shield last?
Insect Shield's EPA label rates apparel for up to 70 washings (25 for some gear). Independent studies found faster fading: one lab study measured permethrin down 28% after 5 washes and about 82% after 30, and a two-year field trial found protection against tick bites dropped from 82% in the first year to 34% in the second. Plan on a season or two of strong protection.
Sources: Sawyer permethrin product page and care guidance (October 2025); Insect Shield EPA label 74843-2 and FAQ; EPA, Repellent-Treated Clothing (February 2026); National Pesticide Information Center; US Army Public Health Center ACU permethrin fact sheet (2017); Armed Forces Pest Management Board Technical Guide 36; Banks et al. 2015; Richards et al. 2018; Connally, Eisen et al. 2019; Vaughn, Meshnick et al. 2014; Richards, Meshnick et al. 2022; CDC tick-bite prevention guidance.