FAQ Permetherin

Permethrin FAQs

Q. How do I use Permethrin safely?

A. Permethrin is to be applied to clothing and material. It works by bonding to the fibers. When a tick or other insect comes into contact with the Permethrin it absorbs a dose that will either repel or kill the insect. You apply Permethrin using an aerosol or pump spray, or use the soak system until the fabric is damp and then allow it to dry. Permethrin is easy to use and the resulting layer of protection is very important to your safety from insect-borne diseases.

Q. Is Permethrin dangerous to my skin?

 A.The warning labels on the cans or bottles are often misunderstood. Your skin metabolizes, or breaks down Permethrin within fifteen minutes of contact with skin. Therefore, it is of no value to you as a personal protection insect repellent when applied to the skin. In addition, the EPA precautionary statement, "Do Not Apply to Skin" indicates that Permethrin is ineffective when applied to skin; therefore, do not apply to skin.

Q. Can I use Permethrin on my cat or dog?

A.Sawyer® Permethrin Clothing Treatments are registered with the US EPA for use on outer clothing and personal gear items, such as sleeping bags, tents and netting. There are other Permethrin formulations registered for use on cats and dogs. Be sure to read the product label to ensure the product can be used on pets.

Q. How long does Permethrin last?

 A.At the concentration level delivered in the aerosol, non-aerosol pump sprays and soak systems (all at 0.5% Permethrin), an application lasts for six weeks and through six washings. Permethrin breaks down through exposure to air (oxygen) and sunlight (ultraviolet light). If you store the clothes in black plastic bags between uses, you can extend the time of effectiveness; however, always retreat after the sixth laundering. Permethrin may also be used on sleeping bags, tents and nettings.

Q. Does Permethrin work against mosquitoes?

 A.Yes. Permethrin clothing treatments, when applied following Directions for Use, have been determined to have "spatial repellency" against mosquitoes. This means that mosquitoes will swarm around you, but not light on your treated clothing and bite.

Also use an EPA registered repellent, such as the Sawyer® microencapsulated Controlled Release 20% DEET, on all exposed skin for further protection from biting and blood sucking mosquitoes.

The combination of Permethrin on clothing and DEET repellent on skin forms an "Insect Repellent System." When used as directed on the EPA registered labels, the Insect Repellent System will provide the best protection from biting, blood sucking and disease carrying insects. A well known study conducted by Tom Lillie, Carl Schreck and A. J. Rahe in Alaska in 1987, showed 99.9% effectiveness against mosquitoes biting at a rate of more than 1,100/hr. This protection is far greater than either a DEET based insect repellent or Permethrin can achieve alone.

Q. Does Permethrin work against bed-bugs?

A.An area bomb which fumigates the room as a whole is usually recommended as the first line of defense against bed bugs. As you may not be in a position to bug bomb your hotel room while traveling abroad (without offending the natives), the following uses for Permethrin may help:

Spray treat at least the upper surfaces of your mattress when you first arrive, with 0.5% Sawyer Permethrin Insect Repellent. Permethrin pump sprays are preferred because they are not restricted for airline travel. Allow the mattress to dry and air out before using it. Cover with a clean sheet for sleeping; do not sleep directly on the treated mattress. If you are concerned about the pillows, uncover them and lightly spray treat them with Permethrin also, re-covering them before use. Use 0.5% Permethrin spray as a residual surface insecticide for cracks and crevices around the room, and as a light spray on stuffed furniture, carpeting, and other fabrics around your sleeping quarters, where bed bugs and other crawling insects may hide.

Some of the information on bed-bugs was extrapolated from Maine University's Pest Management's Fact Sheet on Bed-Bugs at

Q. Will Permethrin ruin my clothes or equipment?

 A.No. Permethrin will not damage clothes or equipment. Unlike DEET, which may harm some fabrics and materials, Permethrin is compatible for use even on fragile fabrics such as silk, plus all synthetics and waterproof membrane fabrics. Permethrin will not affect plastics or finishes. IF IN DOUBT, try a sample on an obscure surface area, especially on delicates and check it after 24 hours of exposure.

Sawyer® Permethrin Insect Repellent is odorless, non-greasy and non-staining after it dries. Permethrin can be harmful to aquatic creatures such as fish, so do not spray Permethrin around fish aquariums.

Q. Can Permethrin be used to keep head lice off headphones?

 A.Over the counter Permethrin products carry the statement that Permethrin is a clothing treatment only, and is not to be worn next to the skin. Permethrin is labeled for clothing treatment only and is not to be applied to, or come in direct contact with the skin. This is because, while there are no known side effects of Permethrin usage, no long-term (40 year) studies have been done to determine if there are any long-term usage effects. Therefore, Permethrin should not be used on headphones or headphone foam coverings, or in any manner not specifically indicated on the product label.

Q. Will Permethrin bond to Cuben Fiber?

A.Cuben Fiber is a high tech laminated material. The top layer is polyester which permetherin will bond to; however, permethrin will not bond to the inner layers of Cuben Fiber. Therefore, permethrin cannot be applied to Cuben Fiber the same way it is applied to other fibers. It will (depending on the size of the material) probably take a few "wettings" to get the necessary 3 ounces dose of permetherin onto the fabric.

To apply permethrin correctly use this process spray the object, let it dry, spray again, let it dry, and spray again. If unabsorbed permethrin drips off the Cuben Fiber catch the drippings and reuse the permethrin. Apply as evenly as possible to the Cuben Fiber until the 3 ounce application is fully absorbed.

The Following Questions Regarding the Use of Permethrin Aerosol Insect Repellent Are Answered By: Hubert L. Snodgrass Senior Toxicology Consultant Scientific Coordination Inc.

1. Does permethrin cause cancer?

 There is no epidemiological evidence to suggest that permethrin causes cancer in humans. Permethrin underwent over 15 years of testing and literally hundreds of toxicity studies before the U.S. Environmental Protection Agency (EPA) approved it for use by the public as a fabric treatment. Seven lifetime studies in animals (cancer assays) were performed. The EPA requested the FIFRA Scientific Advisory Panel, a group of independent experts, to review the collective data and assess the cancer-causing potential of permethrin. The panel concluded that: "...based on all the data together, the oncogenic potential of Permethrin [likelihood of producing tumors] was very weak. The possibility of oncogenic potential in man was extremely remote." The U.S. Army also commissioned an independent review by the National Academy of Sciences (NAS) to assure permethrin's safety for military personnel. Regarding the issue of permethrin carcinogenicity, the NAS noted: "Therefore, the subcommittee concludes that permethrin-impregnation of BDUs [Battle Dress Uniforms] is not a serious carcinogenic risk to field or nonfield military personnel or to garment workers."

2. Does permethrin cause reproductive effects?

Several animal developmental and reproductive studies (up to three generations) have demonstrated the absence of effects on male or female parents, or their offspring, except at exorbitant doses. There are no scientific grounds to suggest that permethrin causes infertility or teratogenic effects in offspring.

3. Does permethrin kill fish?

Permethrin is toxic to fish and should not be disposed of in waterways. The greatest danger to fish is from accidental spills of permethrin in quantity. Empty permethrin containers must be disposed of in a landfill. Residues from permethrin-treated clothing are not an environmental hazard since leaching of the chemical from fabric is negligible.

4. Does permethrin ever leave the environment?

Permethrin breaks down quickly in the environment. The vapor phase reacts with sunlight to degrade the chemical within a few hours. If released to soil, permethrin is expected to have no mobility. Some will be broken down quickly as a vapor, while the remaining chemical will be absorbed by the soil and biodegraded in less than four weeks. If released into moving water, permethrin is expected to absorb to suspended solids and sediments. Degradation would occur within a few days.

5. Does permethrin on clothing contribute to making super bugs?

Permethrin does not increase the biting behavior or aggressiveness of the target insects (arthropods) it is intended to repel or kill.

6. How much permethrin comes off the clothing when laundered?

A strong bond is formed between permethrin and most fabrics. In fact, some insect repellency was observed in military uniforms following 50 launderings. However, the uniforms were treated using an absorption method instead of the aerosol can. In studies performed by the U.S. Army, about 20 to 30 percent of the permethrin treatment was removed after the first laundering. Thereafter, about 3 to 5 percent was lost to each cycle through ten launderings.

7. Where does the permethrin go once it is in the water? How harmful is it once it is in the water?

See 3 and 4 above.

8. What was the association of permethrin with the Gulf War Syndrome?

Research into the causes of Gulf War Illness looked at every possible chemical and/or drug that military personnel may have been exposed to during the conflict. There were literally hundreds of substances, and combinations thereof, examined. The 0.5 percent permethrin aerosol was available to personnel in-country during the 1991 war, but its use was minimal since most action occurred during the winter months when insect populations were low or nonexistent. To date, no substantive evidence exists to implicate permethrin as a cause of Gulf War Illness.

9. How harmful is the wet permethrin right after applying it to clothing?

The directions for applying permethrin from the aerosol can to clothing state that the fabric should be allowed to dry before wear or handling. However, contact with the wet material should pose minimal concern but should be washed off. The amount of permethrin available for skin absorption is very low and is not expected to cause adverse effects.

10. Once dry will permethrin leave clothes and enter your skin and how harmful is that?

All substances that contact the skin surface are absorbed to some extent, whether they are fabric finishes, cosmetics, sunscreens, or insect repellents. Studies performed by the U.S. Army have shown that about 0.5 percent per day of the permethrin in fabric may reach the skin surface of the wearer. However, since skin absorption of permethrin in humans is less than 2 percent, this amounts to a negligible absorbed dose. The EPA used these values in calculating permethrin absorption from wearing treated clothing and considers the human health effects acceptable.

11. How harmful are permethrin fumes while treating clothing?

It is recommended that treating clothing with the permethrin aerosol be performed outdoors. If the treatment is accidentally carried out indoors, no adverse health effects are expected based upon calculations of inhaled dose. However, individuals with breathing problems, such as asthma, may be at greater risk. The odor arising from treating fabric with permethrin is mostly from the aerosol propellants rather than from the insect repellent itself.

12. Can permethrin cause skin irritation or sensitization from repeated use?

Studies in animals have demonstrated that no skin irritation or sensitization is expected following direct application. In a controlled human study, permethrin did not cause significant skin irritation or sensitization when tested in 200 subjects. No significant skin effects are expected from wearing permethrin-treated clothing.

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