Subscribe to the wiseGEEK Feed

What is Permethrin?

Permethrin is a broad-spectrum contact insecticide which kills a wide variety of arthropods on contact, including fleas, ticks, scabies, lice, and bees, among many others. This product is sold for a variety of purposes, ranging from flea control in dogs to treatments for wood to deter damage from boring insects. Some caution is advised when using permethrin, as it is fatal to cats and fish, and it has been linked with tumors in laboratory animals.

Historically, permethrin was derived from chrysanthemums, but by the 1970s, it was being produced synthetically. This insecticide works as a neurotoxin, overstimulating the nervous system of insects which come into contact with it. Once of the problems with permethrin is that it is an indiscriminate pesticide, killing all insects which come into contact with it, including beneficial arthropods. Mammals are also at risk of developing health problems if they ingest permethrin or are exposed to large amounts of it, and some people experience violent allergic reactions when they use permethrin to treat parasitic infestations.

Several companies manufacture permethrin in a wide variety of formats. Permethrin sprays can be used to treat a wide area for insects, and such sprays are sometimes used by campers and aid organizations working in developing nations to keep insects out of beds and clothing. Permethrin is also used in the treatment of some wood to prevent insect infestation.

In medical use, topical applications of permethrin are used to prevent fleas in dogs, although pet owners should be aware that permethrin products should never be used on cats. Permethrin creams and lotions are also available to treat lice, scabies, and other parasitic infestations in humans. Typically, only one application is required, as permethrin will persist through several washings.

Before using a permethrin product to treat a parasitic infestation, it is a good idea to discuss your health with your doctor. Permethrin can interact poorly with some medications, and it is also not advised for use by pregnant women and nursing mothers. A history of allergies, asthma, and some other conditions may also contraindicate the use of permethrin.

When using permethrin to treat wood, garments, tents, and so forth, it is important to be aware that this type of permethrin is not intended for topical use in humans and other animals, because it is very strong. It is a good idea to allow the material to dry completely after an application of spray to avoid coming into direct contact with the permethrin, and wearing gloves during the spraying process can be advisable as well. A permethrin application will typically endure for two weeks or two washings, whichever comes first.

Written by S.E. Smith