News from CRIS: Insect Repellent - Permethrin

July 10, 2023

What are insect repellents?

Insect repellents are products that help prevent, repel, or mitigate pests. These can be products that we apply to our skin or products like lanterns or candles that use a heating mechanism to disperse repellents (1).

This post will focus on the community-requested ingredient permethrin, used as an insect repellent.

What do I need to know about insect repellents?

Manufacturers design different types of insect repellents to repel various insects. Disease-carrying insects, specifically ticks and mosquitoes, are the most common targets of insect repellents.

The U.S. Environmental Protection Agency (EPA) is responsible for the regulation of insect repellents, including permethrin.

Do all insect repellents work?

There are two kinds of insect repellents:

  • EPA-registered products that have been tested for efficacy and safety.

  • Unregistered products that have been tested only for safety.

EPA-registered products are tested to ensure they repel mosquitoes and/or ticks and are safe when used as directed. The EPA recommends using these products when you’re trying to avoid disease-carrying insects.

Unregistered products are tested to ensure safety, meaning if someone uses the products, including vulnerable populations like children and pregnant women, the product is unlikely to cause undue harm. Unregistered products are not tested to ensure efficacy (1,2).

What is permethrin?

Permethrin is a synthetic chemical compound that belongs to the class of pyrethroids. Pyrethroids are synthetic versions of natural insecticides found in chrysanthemum flowers (1).

We find permethrin in many insecticides and insect repellents designed to deter or destroy insects (1). Permethrin is frequently used in the creation of pre-treated insect-repelling fabrics (1).  

Permethrin is also used as a treatment for lice and scabies. However, this post will focus on its insect-repellent uses.

What does permethrin do?

Permethrin is commonly used to control and eliminate a variety of pests, including mosquitoes, ticks, fleas, mites, and lice. It acts by interfering with the nervous system of insects, leading to paralysis and eventual death. Permethrin is effective against both adult insects and their larvae (1,2).

Can permethrin cause adverse reactions?

Permethrin is minimally toxic to humans and most mammals when used as directed. It breaks down rapidly in the environment, especially when exposed to direct sunlight (1).

However, it is still important to follow safety instructions and avoid excessive exposure or ingestion.

Although rare, insect-repellent products, including permethrin, can cause some people to have skin irritation or reactions. In that case, you should wash the area to remove any product, discontinue use, and contact a medical professional if it is severe.


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