Permethrin Facts

Permethrin Fact Sheet: Did you know?

Download the Permethrin Fact Sheet PDF

What is permethrin?

  • It is a stable (synthetic) form of an insecticidal compound produced by the chrysanthemum flower.
  • It is commonly used to treat lice (Nix 1% shampoo) and scabies infections (5% cream).
  • It biodegrades quickly in contact with soil and water.
  • It is odorless and will not stain clothing.

How well does it work?

  • It has been used as a clothing treatment to prevent bites from ticks, flies, and mosquitoes since the 1970s, and used by the military since the 1990s.
  • It provides a quick tick knock-down effect – both repels and kills.
  • A URI study found that people wearing permethrin-treated sneakers and socks were 73.6 times less likely to have a tick bite than those wearing untreated footwear.
  • Each at-home treatment lasts for roughly 3-4 weeks (with washing!).
  • Commercially-treated clothes can last up to 70 washes.

Should I be concerned about using this chemical?

  • Permethrin is over 2,250 times  more  toxic to ticks than humans.
  • Put directly on the skin, typically less than 1% of active ingredient is absorbed into the body;  DEET  can be absorbed at over  20 times  that rate.
  • Exposure risk of permethrin-treated clothing to toddlers is  27 times below  the EPA's Level of Concern (LOC).
  • A 140-pound person would have no adverse health effects if exposed to 32 grams of permethrin/day. There is less than 1 gram of permethrin in an entire bottle of clothing treatment.
  • Permethrin is pregnancy category B (showing no evidence of harm to fertility or fetus).

**Caution: Permethrin won’t hurt humans or dogs but it is harmful to bees, fish, and aquatic insects – do not spray clothing near flowers or water sources. Do not allow cats near permethrin-treated clothing until it has fully dried.

Sources:

  • United States Environmental Protection Agency. 2006.  Permethrin Facts.
  • http://www.epa.gov/oppsrrd1/REDs/factsheets/permethrin_fs.htm
  • Toynton K, Luukinen B, Buhl K, Stone D. 2009.  Permethrin General Fact Sheet; National Pesticide Information Center, Oregon State University Extension Services. http://npic.orst.edu/factsheets/PermGen.html
  • Miller NJ, Rainone EE, Dyer MC, Gonzalez ML, Mather TN. 2011. Tick bite protection with permethrin-treated summer-weight clothing. J. Med. Entomol. 48(2):327-333. http://www.tickencounter.org/pub/tick_repellent_clothing.pdf