Mosquitos: How to Choose Use Insect Repellents Safely

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How to Choose and Use Insect Repellents

Mosquitoes, biting flies, and ticks can be annoying and sometimes pose a serious risk to public health. In certain areas of the United States, mosquitoes can transmit diseases like equine, West Nile Virus and St. Louis encephalitis. Biting flies can inflict a painful bite that can persist for days, swell, and become infected. Ticks can transmit serious diseases like Lyme disease, West Nile Virus, and Rocky Mountain spotted fever. When properly used, insect repellents can discourage biting insects from landing on treated skin or clothing.

Why You Should Use Mosquito Repellent

Insect repellent helps reduce your exposure to mosquito bites that may carry West Nile virus or other diseases, and allows you to continue to play, work, and enjoy the outdoors with a lower risk of disease.

When You Should Use Mosquito Repellent

Use repellent when you go outdoors. You should use repellent even if you're only going outside for a few minutes. Many of the mosquitoes that carry the West Nile virus bite between dusk and dawn. If you're outside during these hours pay special attention to using repellent.

Which Mosquito Repellents Work Best

A wide variety of insect repellent products are available. CDC recommends the use of products containing active ingredients which have been registered with the U.S. Environmental Protection Agency (EPA) for use as repellents applied to skin and clothing.

When EPA registers a repellent, they evaluate the product for efficacy and potential effects on human beings and the environment. EPA registration means that EPA does not expect a product, when used according to the instructions label, to cause unreasonable adverse effects to human health or the environment.

Of the active ingredients registered with the EPA, two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature.* Products containing these active ingredients typically provide longer-lasting protection than others:

  • DEET (N,N-diethyl-m-toluamide)
  • Picaridin (KBR 3023)

Oil of lemon eucalyptus [p-menthane 3,8-diol (PMD)], a plant based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the US it provided protection similar to repellents with low concentrations of DEET.

These recommendations are for domestic use in the United States. See CDC Travelers' Health website for specific recommendations concerning protection from insects when traveling outside the United States.

In addition, certain products which contain permethrin are recommended for use on clothing, shoes, bed nets, and camping gear, and are registered with EPA for this use. Permethrin is highly effective as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial products are available pretreated with permethrin. Permethrin is not to be used directly on skin.

How Often You Should Re-apply Repellents

Follow the directions on the product you are using. Sweating or getting wet may mean that you need to re-apply more frequently.

How the Percentage of Active Ingredient in a Product Relates to Protection Time

In general, the more active ingredient (higher percentage) it has, the longer a repellent will protect you from mosquitoes. For example, DEET products are available in many formulations--something with 30% DEET will protect you longer than one with 5% DEET. You cannot directly compare the percentage of one active ingredient to another, however.

Use your common sense. Re-apply repellent if you start to get bitten and follow the label instructions.

As a "rule of thumb":

  • For many hours outside (over 3-4 hours) and/or where biting is very intense-look for a repellent containing more than 20% DEET. Products with more than 50% DEET do not offer additional protection.
  • For shorter periods of time, repellents containing less than 20% DEET, the repellent currently available with 7% picaridin or one of the products containing oil of lemon eucalyptus may provide adequate protection. There are other products available, but they may not protect as long as those named here.
  • Even if you're going out for 10 minutes use a repellent -that's long enough to get bitten!

Hint: Applying permethrin to your clothing ahead of time will give you even greater protection.

Remember-if you're getting bitten, do something about it!

Choose a repellent that you will use consistently. Also, choose a product that will provide sufficient protection for the amount of time that you will be spending outdoors. Product labels often indicate the length of time that you can expect protection from a product. If you are concerned about using insect repellent, consult your health care provider for advice.

DEET

How the Percentage of DEET in a Product Relates to Protection Time

Typically, the more active ingredient a product contains the longer it provides protection from mosquito bites. The concentration of different active ingredients cannot be directly compared (that is, 10% concentration of one product doesn't mean it works exactly the same as 10% concentration of another product.)

DEET is an effective active ingredient found in many repellent products and in a variety of formulations. Based on a 2002 study (Fradin and Day, 2002.):

  • A recent study indicates the following:
  • 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 with 6.65% DEET provided almost 2 hours of protection.
  • Products with 4.75% DEET were both able to provide roughly 1 and a half hour of protection.

These examples represent results from only one study and are only included to provide a general idea of how such products may work. Actual protection will vary widely based on conditions such as temperature, perspiration, and water exposure.

Choose a repellent that provides protection for the amount of time that you will be outdoors. A product with a higher percentage of active ingredient is a good choice if you will be outdoors for several hours while a product with a lower concentration can be used if time outdoors will be limited. Simply re-apply repellent (following label instructions) if you are outdoors for a longer time than expected and start to be bitten by mosquitoes.

Other repellents

CDC recommends products containing active ingredients which have been registered with US Environmental Protection Agency (EPA) for use as insect repellents on skin or clothing.

All of the EPA-registered active ingredients have demonstrated repellency however some provide more longerlasting protection than others. Additional research reviewed by CDC suggests that repellents containing DEET (N,N-diethyl-m-toluamide) or picaridin (KBR 3023) typically provide longer-lasting protection than the other products and oil of lemon eucalyptus (p-menthane-3,8-diol) provides longer lasting protection than other plant-based repellents. Permethrin is another long-lasting repellent that is intended for application to clothing and gear, but not directly to skin. In general, the more active ingredient (higher concentration) a repellent contains, the longer time it protects against mosquito bites.

People who are concerned about using repellents 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

How can you know which active ingredient a product contains?

Certain products which contain permethrin are recommended for use on clothing, shoes, bed nets, and camping gear, and are registered with EPA for this use. Permethrin is highly effective as an insecticide and as a repellent. Permethrin-treated clothing repels and kills ticks, mosquitoes, and other arthropods and retains this effect after repeated laundering. The permethrin insecticide should be reapplied following the label instructions. Some commercial products are available pretreated with permethrin.

Using Products Containing DEET Safely on Children

Repellent products must state any age restriction. If there is none, EPA has not required a restriction on the use of the product.

According to the label, oil of lemon eucalyptus products should NOT be used on CHILDREN UNDER 3 YEARS.

In addition to EPA's decisions about use of products on children, many consumers also look to the opinion of the American Academy of Pediatrics (AAP). The AAP does have an opinion on the use of DEET in children (see below). AAP has not yet issued specific recommendations or opinion concerning the use of picaridin or oil of lemon eucalyptus for children. CDC will post a link to such information from the Academy when/if it becomes available.

Since it is the most widely available repellent, many people ask about the use of products containing DEET on children. 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 to manufacturer's recommendations.

The American Academy of Pediatrics (AAP) Committee on Environmental Health has updated their recommendation for use of DEET products on children in 2003, 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." AAP recommends that repellents with DEET should not be used on infants less than 2 months old.

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.

If you are concerned about using repellent products on children you may wish to consult a health care provider for advice or contact the National Pesticide Information Center (NPIC) through their toll-free number, 1-800-858-7378 or npic.orst.edu

Always follow the recommendations appearing on the product label when using repellent on children.

  • 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 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.

In addition to wearing repellent, you can protect yourself and your family by taking these precautions:

  • Wear clothing with long pants and long sleeves while outdoors. Apply DEET or other repellents such as permethrin to clothing, as mosquitoes may bite through thin fabric. (Remember: don't use permethrin on skin.)
  • Use mosquito netting over infant carriers.
  • Reduce the number of mosquitoes in your area by getting rid of containers with standing water that provide breeding places for the mosquitoes.

Using Insect Repellents Safely

  • Always follow the instructions on the product label.
  • Apply repellents only to exposed skin and/or clothing (as directed on the product label.) Do not use repellents under clothing.
  • Never use repellents over cuts, wounds or irritated skin.
  • Do not apply to eyes or mouth, and apply sparingly around ears. When using sprays, do not spray directly on face-spray on hands first and then apply to face.
  • Do not allow children to handle the product. When using on children, apply to your own hands first and then put it on the child. You may not want to apply to children's hands.
  • Use just enough repellent to cover exposed skin and/or clothing. Heavy application and saturation are generally unnecessary for effectiveness. If biting insects do not respond to a thin film of repellent, then apply a bit more.
  • After returning indoors, wash treated skin with soap and water or bathe. This is particularly important when repellents are used repeatedly in a day or on consecutive days. Also, wash treated clothing before wearing it again. (This precaution may vary with different repellents-check the product label.)
  • If you or your child get a rash or other bad reaction from an insect repellent, stop using the repellent, wash the repellent off with mild soap and water, and call a local poison control center for further guidance. If you go to a doctor because of the repellent, take the repellent with you to show the doctor.

Note that the label for products containing oil of lemon eucalyptus specifies that they should not to be used on children under the age of three years.

Other than those listed above, EPA does not recommend any additional precautions for using registered repellents on pregnant or lactating women, or on children.

Can I use an insect repellent and a product containing sunscreen at the same time? What are the recommendations for combination sunscreen/insect repellent products ?

Yes. People can, and should, use both a sunscreen and an insect repellent when they are outdoors. Follow the instructions on the package for proper application of each product. In general, the recommendation is to apply sunscreen first, followed by repellent.

It is recommended NOT to use a single product that combines insect repellent containing DEET and sunscreen, because the instructions for use of insect repellents and use of sunscreen are different. In most situations, insect repellent does not need to be reapplied as frequently as sunscreen. While no recommendations are available at this time regarding products that combine other active ingredients and sunscreen, it is important to always follow the label on whatever product you are using.

To protect from sun exposure and insect bites, you can also wear long sleeves and long pants. You can also apply insect repellent to your clothing, rather than directly to your skin.

Important Information on Using Pesticides

EPA recommends the following precautions when using an insect repellent or pesticide:

  • Check the container to ensure that the product bears an EPA-approved label and registration number. Never use a product that has not been approved for use by EPA!

  • Read the entire label before using a pesticide. Even if you have used it before, read the label again - don't trust your memory.

  • Follow use directions carefully, use only the amount directed, at the time and under the conditions specified, and for the purpose listed. For example, if you need a tick repellent, make sure that the product label lists this use. If ticks are not listed, the product may not be formulated for that use.

  • Store pesticides away from children's reach, in a locked utility cabinet or garden shed.

For more, please visit the following areas:

The above information has been provided with the kind permission of the Centers for Disease Control (www.cdc.gov).


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Reviewed on 7/24/2006

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