The Two-Layer System: Permethrin on Clothing, Repellent on Skin
The CDC recommends two layers of bite protection: treat clothing and gear with 0.5 percent permethrin, or buy pre-treated versions, then apply an EPA-registered insect repellent such as picaridin to exposed skin. The treated fabric protects what it covers. The skin repellent covers the rest. And the CDC instructs that permethrin products never go directly on skin.
What are the two layers, and why do health agencies pair them?
CDC tick guidance comes in two parts. First, treat clothing and gear with products containing 0.5 percent permethrin, which the CDC says can be used on boots, clothing, and camping gear and remains protective through several washings; buying pre-treated clothing and gear works too. Second, use an EPA-registered insect repellent on skin. Picaridin is among the named active ingredients, alongside DEET, IR3535, oil of lemon eucalyptus, para-menthane-diol, and 2-undecanone.
The CDC's mosquito guidance stacks the same steps as separate line items: use an EPA-registered insect repellent, wear loose-fitting, long-sleeved shirts and pants, and wear clothing and gear treated with permethrin. Its tick messaging gets specific about what to treat: boots, pants, socks, and tents, or clothing pre-treated with permethrin.
The EPA explains why the pairing matters. Permethrin-treated clothing protects only the skin surface the fabric covers, so the agency advises treating other exposed parts of the body with a repellent labeled for use on human skin for more complete protection. One layer lives on the fabric, one on the skin. If ticks are your main concern, our guide to when tick season starts and peaks covers the timing side.
How does permethrin work, and how is a skin repellent different?
The CDC describes permethrin as an insecticide that kills or repels mosquitoes. The CDC Yellow Book goes further, calling it a highly effective insecticide, acaricide (a pesticide that kills mites and ticks), and repellent. The EPA classifies it as a broad spectrum synthetic pyrethroid insecticide, and notes that when used to pre-treat clothing, it is an insect repellent.
Permethrin sits in the pyrethroid family, synthetic chemicals that act like natural extracts from the chrysanthemum flower, per the National Pesticide Information Center (NPIC). It can affect insects that touch it or eat it, acting on the insect nervous system and causing muscle spasms, paralysis, and death. NPIC notes it is more toxic to insects than to people and dogs because insects cannot break it down as quickly. At the 0.5 percent concentration used on clothing, the Yellow Book says treated fabric repels and kills chiggers, mosquitoes, ticks, and other biting and nuisance arthropods.
The skin layer works on a different principle. Picaridin repels insects and makes them less likely to bite; NPIC says it seems to block mosquitoes from sensing their prey, and it does not kill them. It is a synthetic compound first made in the 1980s, designed to resemble piperine, a natural compound found in the group of plants used to produce black pepper. It can be used on human skin or clothing and repels mosquitoes, biting flies, ticks, fleas, and chiggers.
That is the division of labor: an insecticide that also repels on your clothing, and a repellent that deters without killing on your skin. For a closer look at the skin-layer actives, see our picaridin vs DEET comparison.
Why does permethrin never go on skin?
Three sources, one rule. The CDC's mosquito prevention page instructs: do not use permethrin products directly on skin. The CDC Yellow Book states that permethrin should never be applied to the skin, only to clothing, mosquito nets, or other fabrics as directed on the product label. NPIC says the same thing from the pesticide side: permethrin treatments are intended only for fabrics, should not be applied directly to skin, and only products with specific instructions for treating clothing should be used.
Should you buy factory-treated gear or treat your own?
Permethrin is the only insect repellent currently used for factory treatment of clothing, per the EPA. The agency first registered permethrin in 1979, registered it for use on clothing for the military in 1990, and registered the first consumer-oriented factory-treated clothing products in 2003. NPIC notes the U.S. military has used permethrin to treat combat uniforms for over 20 years to protect soldiers from diseases carried by insects. Per the CDC Yellow Book, factory-treated clothing is labeled for efficacy through many launderings, and the EPA's 2009 revised risk assessment, which evaluated scenarios including toddlers mouthing treated clothing and military personnel wearing treated uniforms daily, found factory-treated clothing unlikely to pose any significant immediate or long-term hazard to the people wearing it.
The DIY route runs through spray-on products the EPA registers for consumers to treat their own clothing against mosquitoes and ticks; the products currently available contain DEET, permethrin, or picaridin. For permethrin sprays, NPIC's instructions are specific: do not apply permethrin to clothing while it is being worn, apply outdoors in well ventilated areas protected from wind, and hang treated fabrics to dry completely before wearing them. The CDC Yellow Book adds that self-treated items must be treated 24 to 48 hours before packing so they can dry, and that label instructions should always be followed. The Yellow Book also notes travelers can treat clothing, hats, shoes, mosquito nets, outerwear, and camping gear with permethrin, and CDC travel packing lists include clothing and gear such as boots, socks, and tents treated with 0.5 percent permethrin.
Durability is where permethrin earns the clothing job. The CDC says permethrin-treated clothing provides protection after multiple washings. The Yellow Book notes treated materials retain repellency or insecticidal activity through repeated launderings and should be retreated as described on the product label. When applied properly, NPIC says, permethrin binds tightly to fabric, with little loss during washing and minimal transfer to the skin; it is the only pesticide the EPA approves for these clothing uses. Clothing treated with skin repellent products such as DEET behaves differently: the Yellow Book says that treatment will not last through washing and requires more frequent application.
The EPA passes along the label's wash-day fine print: small amounts of permethrin can come off in the wash, only outer clothing gets treated (never items like underwear), and treated clothing gets washed separately from non-treated clothing. Our permethrin clothing guide walks through the whole process.
What about cats?
Cat owners run into permethrin warnings and deserve the full picture, including the concentrations involved. NPIC states that cats are more sensitive to permethrin than dogs or people because it takes their bodies a long time to break it down. Its fact sheet describes what accidental exposure to high concentration products can do: cats exposed to products with 45 to 65 percent permethrin may seem anxious, may be unable to walk normally, may have muscle tremors and seizures, and may die from the exposure.
Read those numbers carefully. The caution describes products in the 45 to 65 percent range. The clothing treatments in CDC guidance contain 0.5 percent permethrin, and the EPA notes the amount of permethrin allowed in clothing is very low. That does not erase the sensitivity NPIC describes, so the Yellow Book's standing advice applies: as with all pesticides, follow the label instructions.
Which repellents belong on the skin layer?
The CDC calls an EPA-registered insect repellent the best way to prevent mosquito bites. Its active ingredient list for skin: DEET, picaridin (known as KBR 3023 and icaridin outside the United States), IR3535, oil of lemon eucalyptus, para-menthane-diol, and 2-undecanone. On the EPA's roster of skin-applied repellent ingredients, picaridin appears in about 40 registered products.
The registration itself carries information. An EPA registration number on the label means the company provided EPA with technical information on the effectiveness of the product.
Application rules from the Yellow Book: apply repellents only to exposed skin or clothing, as directed on the product label, and not to skin covered by clothing. In general, higher concentrations of active ingredients provide longer protection, regardless of the active ingredient. Building a kit for the trail? Our hiking repellent guide puts both layers together.
On the skin layer, a note about ours: Longsleeve is an EPA-registered picaridin lotion (EPA Reg. No. 101457-1). It repels mosquitoes and ticks for up to 14 hours. It is fragrance-free, with nine disclosed ingredients.
Frequently asked questions
Can permethrin go on skin if I run out of repellent?
No. The CDC instructs: do not use permethrin products directly on skin. The CDC Yellow Book says it should never be applied to the skin, only to clothing, mosquito nets, or other fabrics as directed on the product label.
How many washes does a permethrin treatment survive?
The CDC says treated clothing remains protective through several washings, and factory-treated clothing is labeled for efficacy through many launderings. The Yellow Book advises retreating as described on the product label for continued protection.
Can children use the skin-layer repellents?
Per the CDC Yellow Book, insect repellents containing DEET, picaridin, IR3535, and 2-undecanone can be used on children without age restriction. Use them as directed on the product label, and talk to your pediatrician if you have questions about a specific child.
Sunscreen and repellent: which goes on first?
The CDC Yellow Book advises using separate products, applying sunscreen first, and then applying the repellent.
If my clothes are treated, do I still need repellent on skin?
Yes, for exposed skin. The EPA notes that treated clothing protects only the skin surface it covers, and advises treating exposed parts of the body with a repellent labeled for use on human skin for more complete protection.
Sources
- CDC, Preventing Tick Bites: https://www.cdc.gov/ticks/prevention/index.html
- CDC, Preventing Mosquito Bites: https://www.cdc.gov/mosquitoes/prevention/index.html
- CDC, Tick Bite Prevention Press Kit: https://www.cdc.gov/ticks/communication-resources/press-kit.html
- CDC, Preventing Mosquito Bites While Traveling: https://www.cdc.gov/mosquitoes/prevention/preventing-mosquito-bites-while-traveling.html
- CDC Yellow Book, Mosquitoes, Ticks, and Other Arthropods: https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/mosquitoes-ticks-and-other-arthropods.html
- EPA, Repellent-Treated Clothing: https://www.epa.gov/insect-repellents/repellent-treated-clothing
- EPA, Skin-Applied Repellent Ingredients: https://www.epa.gov/insect-repellents/skin-applied-repellent-ingredients
- National Pesticide Information Center, Permethrin General Fact Sheet: http://npic.orst.edu/factsheets/PermGen.html
- National Pesticide Information Center, Permethrin Treated Clothing: http://npic.orst.edu/pest/mosquito/ptc.html
- National Pesticide Information Center, Picaridin General Fact Sheet: http://npic.orst.edu/factsheets/PicaridinGen.html
Last reviewed 2026-08-17 · every claim on this page is sourced above