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West Nile Virus Insect Repellant Q & A
Mosquito Dusk to Dawn

Q: What time of day should I wear mosquito repellent?
A: Many of the mosquitoes that carry the West Nile virus are especially likely to bite in the evening and early morning hours. If you are outdoors around these times of the day, it is important to apply repellent. In many parts of the country, there are mosquitoes that also bite during the day, and these mosquitoes have also been found to carry the West Nile virus. The safest decision is to apply repellent whenever you are outdoors.

Q: How often should repellent be reapplied?
A: Follow the directions on the product you are using in order to determine how frequently you need to reapply repellent. Sweating, perspiration or getting wet may mean that you need to re-apply repellent more frequently. If you are not being bitten, it is not necessary to re-apply repellent. Repellents containing a higher concentration of active ingredient (such as DEET) provide longer-lasting protection.

Q: How does mosquito repellent work?
A: Female mosquitoes bite people and animals because they need the protein found in blood to help develop their eggs. Mosquitoes are attracted to people by skin odors and carbon dioxide from breath. Many repellents contain a chemical, N,N-diethyl-m-toluamide (DEET), which repels the mosquito, making the person unattractive for feeding. DEET does not kill mosquitoes; it just makes them unable to locate us. Repellents are effective only at short distances from the treated surface, so you may still see mosquitoes flying nearby. As long as you are not getting bitten, there is no reason to apply more DEET.

Q: Which mosquito repellent works the best?
A: The most effective repellents contain active ingredients of DEET (N,N-diethyl-m-toluamide) or Picaridin (KBR 3020) which repel pests like mosquitoes and ticks. Repellents containing these ingredients have been tested against a variety of biting insects and have been shown to be very effective. Oil of eucalyptus [p-methane 3,8-diol (PMD)], a plant based repellent has been shown to provide similar protection to lower concentrations of DEET. The more of these active ingredients that a repellent contains the longer time it can protect you from mosquito bites. A higher percentage of DEET or Picaridin in a repellent does not mean that your protection is better—just that it will last longer. DEET concentrations higher than 50% do not increase the length of protection.

Q: Is DEET safe?
A: Yes, products containing DEET are very safe when used according to the directions. Because DEET is so widely used, a great deal of testing has been done. When manufacturers seek registration with the U.S. Environmental Protection Agency (EPA) for products such as DEET, laboratory testing regarding both short-term and long-term health effects must be carried out. Over the long history of DEET use, very few confirmed incidents of toxic reactions to DEET have occurred when the product is used properly. (From the National Pesticide Information Center [NPIC], EPA re-registration eligibility decision.

Q: What are some general considerations to remember in order to use products containing DEET safely?
A: Always follow the recommendations appearing on the product label.
Use enough repellent to cover exposed skin or clothing. Don't apply repellent to skin that is under clothing. Heavy application is not necessary to achieve protection.
Do not apply repellent to cuts, wounds, or irritated skin.
After returning indoors, wash treated skin with soap and water.
Do not spray aerosol or pump products in enclosed areas.
Do not apply aerosol or pump products directly to your face. Spray your hands and then rub them carefully over the face, avoiding eyes and mouth.

Q: How should products containing DEET be used on children?
A: No serious illness has been linked to the use of DEET in children when used according to 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 with a concentration of 30% appear to be as safe as products with a concentration of 10% 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. 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 http://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

Q: Is DEET safe for pregnant or nursing women?
A: There are no reported adverse events following use of repellents containing DEET in pregnant or breastfeeding women.

Q: Can I use an insect repellent and sunscreen at the same time?
A: 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 repellent 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

Q: How does the percentage of an active ingredient in a product relate to the amount of the protection it gives?
A: Based on recent study results:
A product containing 23.8% DEET provided an average of 5 hours of protection from mosquito bites.
A product containing 20% DEET provided almost 4 hours of protection
A product containing 15% DEET provided an estimated average of 7 hours of protection.
A product containing 10% Picaridin provided an estimated average of 5 and a half hours of protection.
A product containing 65% oil of lemon eucalyptus provided an estimated average of 7 and a half hours of protection.
A product with 6.65% DEET provided almost 2 hours of protection
Products with 4.75% DEET and 2% soybean oil were both able to provide roughly 1 and a half hour of protection.
Choose a repellent that provides protection for the amount of time that you will be outdoors. A higher percentage of an active ingredient should be used if you will be outdoors for several hours while a lower percentage of an active ingredient can be used if time outdoors will be limited. You can also re-apply a product if you are outdoors for a longer time than expected and start to be bitten by mosquitoes.

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