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Insect repellent safety refers to the proper use of chemicals applied to the skin or clothing to ward off insects that bite or sting. If they are not used correctly, these substances can sometimes cause serious side effects.

What is the information for this topic?

Many products on the market keep away insects. Of the active ingredients registered with the Environmental Protection Agency (EPA), the Centers for Disease Control and Prevention (CDC) believes that two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature and products containing these active ingredients typically provide longer-lasting protection than others:

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

Permethrin is another long-lasting repellent that is intended for application to clothing and gear, but not directly to skin.

Oil of lemon eucalyptus <active ingredient: 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. Oil of lemon eucalyptus provides longer lasting protection than other plant-based repellents.

The more active ingredient a product contains the longer it provides protection from insect bites. However, 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:

• 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.

According to the CDC, 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.

DEET has been used for over 40 years. DEET and picaridin are both very effective against bites by:

• mosquitoes
• fleas
• ticks
• chiggers
• biting flies

Neither DEET nor other repellents are able to deter stinging insects such as bees, hornets, and wasps. DEET is available in the U.S. in strengths ranging from 4% concentration to 100%. It comes in a variety of forms, including:

• lotions
• sprays
• creams
• gels

For the most part, DEET has a very safe record. An estimated 200 million people around the world use it every year without reported problems. But the chemical is absorbed through the skin, so it can cause a toxic reaction if used in high doses. There have been a few cases of neurologic problems in young children as a result of high doses of DEET.

For this reason:

• The American Academy of Pediatrics recommends that children not use bug repellents containing more than 10% DEET.
• For most purposes, adults using insect repellent should choose concentrations of 30% or less.
• The amount of DEET can vary from one product to another, so it is important to read the label before choosing a bug repellent.
• AAP has not yet issued specific recommendations or opinion concerning the use of picaridin or oil of lemon eucalyptus for children.

It is important to remember that:

• Using DEET at the same time as a sunscreen can prevent the sunscreen from working as well.
• DEET can damage plastics, synthetic fabrics, leather, and painted surfaces, so it should be applied carefully.

The U.S. Environmental Protection Agency (EPA) offers these guidelines for the safe use of all types of insect repellents.

• Apply to exposed skin or clothing only as the package directs. Do not apply repellent under clothing.
• Do not apply to cuts, wounds, or broken skin.
• Keep out of the eyes and mouth. Use only small amounts around the ears. When applying repellent to the face, spray it first into the hands, then rub onto the face.
• Do not let children handle the repellent or get it on their hands. Adults should apply it to children.
• Do not spray in enclosed areas.
• Use just enough to cover exposed skin. Avoid heavy application.
• Wash with soap and water after returning indoors. This is especially important if insect repellent is used day after day. Wash clothes that have been treated as well.

According to CDC, people can, and should, use both a sunscreen and an insect repellent when they are outdoors. The CDC recommends following the instructions on the package for proper application of each product. In general, the CDC recommends to apply sunscreen first, followed by repellent.

The CDC does NOT recommend using 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.

Stop use and call the poison control center if a reaction is suspected. These centers are operated 24 hours a day, 7 days a week. Keep the number and address in an easy-to-reach place. The number for the local poison control center can be found at www.poison.org, the website of the National Capital Poison Center or www.AAPCC.org, the official website of the American Association of Poison Control Centers, or by calling 800-222-1222.