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| What is Permethrin? | ||||||||
| Permethrin is a man-made insecticide, structurally similar to a naturally-occurring chemical called pyrethrum. Pyrethrum was initially derived from the crushed dried flowers of the daisy Chrysanthemum, whose insecticidal properties have been recognized since the 18th century. The permethrin which is currently sold to consumers is a synthesized product that was developed in the 1970's. |
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| How does permethrin work? | ||||||||
| Permethrin works as a contact insecticide, damaging the nervous system of insects which come in contact with it, leading to either their death or "knockdown". Permethrin is effective against multiple species of crawling and flying insects, including mosquitoes, ticks, fleas, bedbugs, chiggers, and flies. Ticks crawling across permethrin-treated pant legs or socks are likely to drop off before they are able to attach and feed. Studies have shown that permethrin-treated bednets can dramatically reduce the risk of getting malaria, through their ability to kill mosquitoes that fly into the treated netting. | ||||||||
| What is the difference between DEET and permethrin? Can I use them interchangeably? | ||||||||
| DEET and permethrin complement one another, but they are not interchangeable. DEET works to repel biting insects, by blocking the receptors on an insect's antennae which help it home in on its host. Permethrin is not an insect repellent. It works as a contact insecticide, stunning or killing insects that come in contact with it. | ||||||||
| Can I use DEET and permethrin together, or is the combination unnecessary? | ||||||||
| When maximum protection against insect bites is needed or desired, the ideal solution is to use a combination of DEET on exposed skin, and wear permethrin-treated clothing. An extended-duration DEET insect repellent (Ultrathon®) and permethrin-treated clothing is the standard personal protection system used by the U.S. military deployed in areas of the world where insect-borne disease is a real threat. One field study showed that the use of both of these products provided 99.9% protection against mosquito bites, in an environment where unprotected persons received an average of 1,188 bites per hour! | ||||||||
| Permethrin should be applied to clothing, or to other fabrics (tent walls, mosquito nets, etc.). It is not intended for direct application to the skin. When treating a garment with permethrin spray, spray the cloth outdoors and allow it to dry before wearing. | ||||||||
| Does permethrin need to be reapplied frequently to keep working? | ||||||||
| No. One of the best things about permethrin is its length of effectiveness per application. When applied to clothing by aerosol or trigger spray, permethrin provides protection lasting up to two weeks or two washings, whichever comes first. Clothing soaked in permethrin solution is effective for up to 4 months per application on stored garments. | ||||||||
| Is permethrin approved for children? | ||||||||
| Permethrin-treated fabrics should be safe for children of any age. Once the permethrin has dried on the clothing, it is bound so tightly to the fibers that any potential for absorption through the skin is negligible. | ||||||||
| Will permethrin damage my clothes? | ||||||||
| No. Permethrin is colorless, odorless, and non-staining. It should not change the feel or look of the clothing to which it is applied. | ||||||||
| Do I have to worry about using it around my pets? | ||||||||
| Permethrin should not be sprayed around ponds or any other areas where fish are found, since the chemical is toxic to fish. Permethrin has not been shown to be toxic to birds. | ||||||||
| Although there are permethrin sprays specifically sold for use on dogs, these products should never be used on cats. Because of their grooming habits and slow metabolism of permethrin, cats are much more susceptible to toxicity from permethrin. Again, once the permethrin has dried on any fabric, toxicity should no longer be of any concern. | ||||||||
| Is there any toxicity associated with permethrin use that I need to worry about? | ||||||||
| Since permethrin is not intended for direct use on the skin, there are very few concerns about toxicity. Any permethrin that might inadvertently get on the skin, however, is very poorly absorbed (less than 2% of the applied dose). Permethrin is rapidly inactivated by skin and liver esterases, and its metabolites are then readily excreted by the kidneys. There is no evidence that permethrin accumulates in human tissues. Although occupational exposure to large amounts of permethrin has been associated with transient symptoms of itching, burning, or numbness, these symptoms have not been reported in consumers applying the products to clothing. Studies have not shown permethrin to be a human teratogen, mutagen, or carcinogen. | ||||||||
| Given that permethrin is an insecticide, am I hurting the environment when I use it? | ||||||||
| Studies have shown that permethrin is environmentally safe. Permethrin is degraded by sunlight, which limits its persistence in the environment. Its half-life is less than 30 days in soil, and the chemical is readily metabolized by soil microorganisms. Once dried on fabric, permethrin is so tightly bound to the fibers themselves, that "leaching" into the environment is essentially not possible. | ||||||||
| Mark S. Fradin, M.D. is Adjucnt Clinical Associate Professor of Dermatology, University of North Carolina/Chapel Hill and the author of Mosquitoes and Mosquito Repellents: A Clinician's Guide. | ||||||||
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