DEET Insect Repellents

DEET (N,N-diethyl-m-toluamide) is a versatile and effective insect repellent. Insect repellents containing DEET have been used for more than 40 years by millions of people worldwide to repel mosquitoes, ticks, fleas, biting flies and chiggers. These products are available in many formulations, including lotions, creams, gels, aerosol and pump sprays, and towelettes. Insect repellents can reduce the risk of mosquito and tick bites, but products containing DEET must be used properly.

Mosquitoes and other blood-feeding flies (such as black flies and deer flies) are attracted to hosts by skin odors and carbon dioxide from their breath. When a mosquito gets close to a host, DEET and some other repellents jam the insect's sensors and confuse the insect so it is unable to land and bite the host successfully. Repellents are effective only at short distances from the treated surface, so the user may still see mosquitoes flying nearby. As long as the user is not getting bitten, there is no reason to apply more DEET.

Ordinarily, the bites of mosquitoes and other insects are just a nuisance, although the bite may cause itching or swelling. The symptoms of an insect bite can usually be treated with over-the-counter medications. However, in rare situations, an insect bite can transmit certain diseases such as West Nile virus, St. Louis encephalitis and California (LaCrosse) encephalitis.

Yes. People can and should use both sunscreen and DEET when they are outdoors to protect their health. Follow the instructions on the package for proper application of each product. Apply sunscreen first, followed by repellant containing DEET. To protect from sun exposure and insect bites, you can also wear long sleeves and long pants. You can also apply insect repellent containing DEET or permethrin to your clothing, rather than directly to your skin.

No. Based on available research, CDC believes it is safe to use both products at the same time. Follow the instructions on the package for proper application of each product. Apply sunscreen first, then insect repellent containing DEET, to be sure that each product works as specified.

Because the instructions for safe use of DEET and safe use of sunscreen are different, CDC does not recommend using products that combine DEET with sunscreen. In most situations, DEET does not need to be reapplied as frequently as sunscreen. DEET is very safe when applied correctly. The rare adverse reactions to DEET have generally occurred in situations where people do not follow the product instructions. Sunscreen often requires frequent reapplication, so using a combined product is not recommended. You do not need to reapply insect repellent every time you reapply sunscreen. Follow the instructions on the package for each product to get the best results.

There has been attention to a study concerning the chemicals in DEET and sunscreen presented at a scientific meeting. This is an in vitro study, which means that it is a laboratory study that did not include human or animal testing. The goal of the study was to examine absorption of these chemicals, and it did not evaluate or make conclusions about health effects related to this issue. The study authors stated that further evaluation of the interaction of these chemicals should be conducted. The study has not yet been published (as of July 2003).

Evaluation by the EPA, which regulates products such as DEET, indicates that it is safe to use insect repellents containing DEET and sunscreen at the same time. CDC recommends using two separate products because sunscreen requires frequent applications while DEET should be used sparingly. Follow the directions on the package for each product, and consult your physician or pharmacist if you have questions. CDC's recommendations for the safe use of insect repellents on children and adults remain unchanged.

• Read and follow the instructions on the label and avoid excessive use and over-application.
• The more DEET a product contains, the longer the repellant can protect against mosquito bites. However, concentrations higher than 50 percent do not increase the length of protection. For most situations, 10 percent to 25 percent DEET is adequate.
• To make sure you will not react to the repellent, apply the product to a small area of skin on your arm or leg before general use.
• Use just enough repellent to cover exposed skin and/or clothing.
• After returning indoors, wash treated skin with soap and water. Wash treated clothing before wearing again.
• Do not spray directly on face; spray the repellent onto hands and then apply to face. Avoid sensitive areas like the eyes, mouth and nasal membranes.
• Do not apply over cuts, wounds or irritated skin.
• Do not use under clothing.
• Avoid spraying on plastics (such as watch crystals and eyeglasses frames), rayon, spandex, other synthetic fabrics, leather and painted or varnished surfaces because DEET can damage those surfaces.
• Do not spray DEET-containing products in enclosed areas.
• DEET products will usually repel mosquitoes for several hours, so it is not necessary to reapply the repellent more frequently than that.
• DEET products will NOT repel stinging insects such as wasps and bees.

No definitive studies exist in the scientific literature about what concentration of DEET is safe for children. No serious illness has been linked to the use of DEET in children when used according the product recommendations. The American Academy of Pediatrics (AAP) Committee on Environmental Health has recently updated their recommendation for use of DEET products on children, citing: "Insect repellents containing DEET (N,N-diethyl-m-toluamide, also known as N,N-diethyl-3-methylbenzamide) with a concentration of 10% appear to be as safe as products with a concentration of 30% when used according to the directions on the product labels."

The AAP and other experts suggest that it is acceptable to apply repellent with low concentrations of DEET to infants over 2 months old. Other guidelines cite that it is acceptable to use repellents containing DEET on children over 2 years of age. Repellent products that do not contain DEET are not likely to offer the same degree of protection from mosquito bites as products containing DEET. Non-DEET repellents have not necessarily been as thoroughly studied as DEET, and may not be safer for use on children.

Parents should choose the type and concentration of repellent to be used by taking into account the amount of time that a child will be outdoors, exposure to mosquitoes, and the risk of mosquito-transmitted disease in the area. Persons who are concerned about using DEET or other products on children may wish to consult their health care provider for advice. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 1-800-858-7378 or npic.orst.edu.
Always follow the recommendations appearing on the product label when using repellent.

• When using repellent on a child, apply it to your own hands and then rub them on your child. Avoid children's eyes and mouth and use it sparingly around their ears.
• Do not apply repellent to children's hands. (Children may tend to put their hands in their mouths.)
• Do not allow young children to apply insect repellent to themselves; have an adult do it for them. Keep repellents out of reach of children.
• Do not apply repellent to skin under clothing. If repellent is applied to clothing, wash treated clothing before wearing again.

Using repellents on the skin is not the only way to avoid mosquito bites. Children and adults can wear clothing with long pants and long sleeves while outdoors. DEET or other repellents such as permethrin can also be applied to clothing (don’t use permethrin on skin), as mosquitoes may bite through thin fabric. Mosquito netting can be used over infant carriers. Finally, it may be possible to reduce the number of mosquitoes in the area by getting rid of containers with standing water that provide breeding places for the mosquitoes.

Before DEET and other repellents may be legally distributed, sold or used in this country, they must be evaluated and registered by the U.S. Environmental Protection Agency (USEPA). When used according to label directions, millions of people have used DEET repellents to provide protection against mosquitoes and ticks with minimal risk. Nevertheless, no repellent is 100 percent safe and all repellents must be used carefully. Use of DEET concentrations above 50 percent have been associated with increased skin irritation and similar reactions. In very rare circumstances, slurred speech, confusion and seizures have been associated with the use of DEET, particularly in children. However, some of these persons had a history of long-term, excessive or improper use of DEET repellents. The risk of experiencing any adverse health effects is reduced when products containing DEET are used according to label instructions and concentrated DEET products are avoided. A fact sheet by USEPA about insect repellents may be found atwww.epa.gov/pesticides/citizens/insectrp.htm. Additionally, an article reviewing DEET and other repellents, "Mosquitoes and Mosquito Repellents: A Clinician's Guide," may be found at www.acponline.org/journals/annals/01jun98/mosquito.htm.

• If you suspect that you or your child is reacting to an insect repellent, discontinue use, wash the treated skin and call your physician or local poison control center. If you go to a doctor or hospital, take the repellent with you. The Illinois Poison Center emergency telephone number is 1-800-222-1222; 312-906-6185 (TTY/TDD).
• Additional information about the active ingredients in repellents and other pesticides may be obtained from the National Pesticide Information Center (NPIC) at 1-800-858-7378 from 8:30 a.m. to 6:30 p.m. (Central time) seven days a week, excluding holidays, or visit NPIC's Web site at http://npic.orst.edu.

If you do not want to use a product containing DEET, or if your physician advises you to avoid DEET, there are other products that can give you limited protection. These repellents generally use plant-based oils to repel insects. In comparison to DEET-based products, plant oil-based repellents are generally effective for a shorter time (usually less than about two hours). Note: Vitamin B, ultrasonic devices and incense have not been shown to be effective in preventing mosquito bites.

Some people use permethrin repellents on clothing to repel ticks, mites and mosquitoes. Permethrin repellents should NEVER be applied to skin; they are to be used on clothing ONLY. Always use permethrin repellents according to the label instructions.

• When permethrin products are applied to clothing, the spray should be allowed to dry before the clothing is worn.
• Permethrin works mainly by killing ticks that come in contact with treated clothes.
• Because treating clothing with permethrin is particularly effective against ticks, they reduce the risk of getting Lyme disease, Rocky Mountain spotted fever and other diseases by preventing tick bites.
• Permethrin is a pesticide and exposure should be minimized. Therefore, it should only be used when ticks or mosquitoes are numerous and other protective measures are not practical or available.

The use of an insect repellent is not the only way to reduce the risk of bites from mosquitoes, ticks and other biting insects that may transmit disease. Other precautions are important as well:

• Avoid places and times when mosquitoes bite. Generally, the peak biting periods occur just before and after sunset and again just before dawn. However some mosquitoes bite during daylight hours in or near shaded or wooded areas.
• Be sure door and window screens are tight-fitting and in good repair.
• Wear appropriate clothing. Long-sleeved tops and long pants made of tightly woven materials keep mosquitoes away from the skin. Be sure, too, that your clothing is light colored. Keep trouser legs tucked into boots or socks.
• Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect small babies at all times.
• Installing bird or bat houses to attract these insect-eating animals has been suggested as a method of mosquito control. However, there is little scientific evidence that this significantly reduces the mosquito population around homes.
• Spraying your backyard with an insecticidal fog or mist is effective only for a short time. Mosquitoes will return when the effect of the spray has ended.
• Insect light electrocutors ("bug zappers") or sound devices do little to reduce biting mosquitoes in an area.

There are no reported adverse events following use of repellents containing DEET in pregnant or breastfeeding women.

Call your local health department or the Illinois Department of Public Health at 217-782-5830. Or visit the Department's Web site and the U.S. Centers for Disease Control and Prevention's West Nile virus site for more information:www.cdc.gov/ncidod/dvbid/westnile/index.htm