How Deet and Permethrin Can Protect You
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First, the bad news: Whatever personal protection you use against ticks, it may not be 100 percent effective. That’s why doing a tick check every day you’re exposed to ticks is so critical, says Neeta Connally, Ph.D., director of the Tickborne Disease Prevention Laboratory at Western Connecticut State University.
The good news: Two substances—deet and permethrin—can go a long way toward keeping you protected, and using at least one is better than not using anything. Deet repels ticks, and permethrin can immobilize them on contact. The Environmental Protection Agency says that when used as directed, both are safe.
Here’s what the research has to say about the benefits and drawbacks of each.
Deet
Deet has been available to the public as a repellent for ticks, mosquitoes, and other pests since 1957. In our tests, we’ve found it to be the most consistently effective. (Our current testing uses only mosquitoes, but past years of testing have shown that repellents that work well against mosquitoes also tend to do well against ticks.)
Deet has proved to be so effective at repelling ticks that it’s often used as the standard to compare the efficacy of newer repellents, says Lars Eisen, Ph.D., a research entomologist in the Centers for Disease Control and Prevention’s Division of Vector-Borne Diseases. Joan Muratore, the test program leader at CR for insect repellents, says, “Our testing has found that deet affords the most reliable protection.”
Pros
It’s versatile. Deet can be applied to skin and clothes (although it shouldn’t be applied under clothes) and comes in a number of formulations that all appear to be effective. We’ve found that lotions, wipes, and aerosol sprays with 25 to 30 percent deet are effective.
It keeps ticks away. Ticks don’t like to touch skin that’s been treated with deet. In a recent study in the journal Ticks and Tick-Borne Diseases, just 3 of 100 ticks successfully walked across a surface treated with a deet solution.
It’s inexpensive. A bottle of deet-based repellent usually costs just $4 to $10.
Cons
It can damage clothes. Deet can damage certain synthetic fabrics (such as rayon and spandex) and plastic (such as watchbands).
It offers short-term protection. To get the full benefit of deet, you need to apply it every single time you might be exposed to ticks. And heavy sweating could affect how long it lasts, according to Connally.
There’s a small margin of error. Repellents with deet need to be applied to all exposed skin, especially arms and legs.
Permethrin
Permethrin, unlike deet, isn’t applied directly to the skin. Instead, you can buy clothing that’s treated with this pesticide. You can also treat your own clothing, shoes, and outdoor gear with permethrin spray, or send them to a company that will treat them for you. CR doesn’t test permethrin, but the Army currently uses uniforms that are treated with it for protection against disease-carrying bugs of all kinds (not just ticks).
It’s less well-known than deet. In a recent nationally representative CR survey, just 14 percent of Americans had ever heard of it. But the CDC has published several recent studies on its tick-disabling properties.
Pros
Requires few applications. According to manufacturers, professionally treated clothing continues to disable ticks even after repeated washings. A 2018 CDC study found that such clothing lost some toxicity to ticks after 16 washes and 16 days of wear but still irritated ticks, causing many to fall off the clothes in lab tests. Clothes you treat yourself lose their toxicity faster but can still be washed several times before needing retreatment.
Convenient. Rather than making sure you’ve sprayed repellent and covered all your exposed skin every time you go out, some people may find it more convenient to start by putting on their permethrin-treated pants, shirt, and shoes. Eisen notes that this is one reason the CDC has been focusing on studying how ticks respond to permethrin-treated clothing.
Cons
Requires planning. If you treat your own clothes and gear, it’s recommended that you take them outside to spray them to avoid inhalation. Clothes should be completely dry before you wear them, which can take 2 to 4 hours.
Can be expensive. Pretreated clothing can be pricey. Pretreated shirts from the company Insect Shield can run from $20 to more than $60.
Toxic to cats. Though permethrin-treated items are safe once completely dry, make sure your cat stays away while you’re spraying. If you have cats and dogs and spot-treat your dogs with permethrin, make sure your cats stay away for 72 hours.
Editor's Note: This article also appeared in the July 2019 issue of Consumer Reports magazine.
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