Permethrin
Cyclopropanecarboxylic acid, 3-(2,2-dichloroethenyl)-2,2-dimethyl-, (3-phenoxyphenyl)methyl ester
What does permethrin actually do?
Permethrin is not a skin repellent. It's an insecticide you apply to clothing and gear, where it kills or knocks down ticks and mosquitoes on contact for about six weeks or six washes. Paired with a skin repellent, treated clothing is the most effective tick defense system available to consumers.
When to choose it: Boots, socks, pants, and packs for hikers, hunters, and anyone in tick country. An RCT among outdoor workers showed major reductions in tick bites.
EPA Substance Registry Services (SRS) listed active ingredient for pesticide products.
The evidence
- Protective effectiveness of long-lasting permethrin-impregnated clothing against tick bites: a randomized controlled trial among outdoor workers2020RctDefinitive evidence
Two-year randomized, placebo-controlled, double-blinded trial of factory permethrin-impregnated clothing versus sham-treated clothing among 82 outdoor workers in an endemic Lyme-disease region.
Common misconceptions
Myth: “Permethrin spray works like bug spray.”
Reality: No. It degrades quickly on skin and isn't labeled for it. Its job is on fabric, applied the night before and allowed to dry.
Myth: “It's too dangerous to use at all.”
Reality: Dried-on-fabric permethrin has a strong human safety record (it's also a prescription scabies treatment). The real cautions: keep wet spray away from cats, and away from waterways.
Regulatory notes
Source: EPA SRS active ingredient list export. Minimum risk (25(b)) status is applied separately when applicable.
Frequently asked questions
How long does permethrin-treated clothing last?
Self-treated clothing holds about 6 weeks or 6 washes; factory-treated garments survive dozens of washes.
Is permethrin safe around pets?
Dried fabric is fine. Wet permethrin is highly toxic to cats, so treat and dry clothing away from them.