Products that prevent insect bites

You can lower your chance of being bitten by an insect by using insect repellents. Mosquitoes, biting flies, and ticks can cause annoying bites and sometimes a serious disease. Mosquito bites can spread infections such as West Nile virus, a virus that causes swelling of the brain (encephalitis), and malaria. Tick bites can cause serious diseases such as Lyme disease and Rocky Mountain spotted fever. Bites from biting flies are painful and may cause a skin infection.

You can buy many different kinds of insect repellents. Some work better than others.¹ It is important for pregnant and nursing women to follow these tips for safe use of insect repellents. If you have a question or concern about the use of insect repellents, talk with your doctor.

Products that work the best

DEET. This repellent works the best. Insect repellents that contain DEET are available in different strengths. Research shows that DEET strengths greater than 50% do not provide much better protection. You get about 5 hours of protection from mosquitoes when you apply an insect repellent to your skin that contains 24% DEET. Wrist, ankle, and neck bands that contain DEET do not work well.

Although there have been concerns about the safety of using DEET on skin, studies over the past 40 years have not shown that DEET causes cancer or other illnesses. Remember these guidelines:

• Do not use DEET on children younger than the age of 2 months.
• When applying DEET to children 2 to 24 months of age:
  • Use only when there is a high risk of insect bites.
  • Use repellents with the lowest concentration of DEET available (usually 5% to 10%).
  • As with all insect repellents, use sparingly and never apply to the hands or near the eyes.
  • Apply no more than one time per day and avoid prolonged use.
• When applying DEET to children 2 to 12 years of age:
  • Use repellents with the lowest concentration of DEET available (usually 5% to 10%).
  • Apply no more than three times per day and avoid prolonged use.

Other things to keep in mind when you use DEET:

• DEET reduces how well sunscreen works by one-third.² If you need to use sunscreen and DEET at the same time, put on sunscreen first and wait 20 minutes before applying DEET.
• Be careful if applying DEET to clothing. It can damage some man-made fabrics, such as nylon and polyester. DEET can also damage plastic watch crystals and eyeglass frames.

Picaridin (KBR 3023). Studies have shown that picaridin works as well as low concentrations of DEET and that no serious toxicity occurs to those who use it. Unlike DEET, picaridin is odorless, does not feel greasy or sticky, is less likely to irritate the skin, and does not damage plastics or fabrics.^{3, 4} The American Academy of Pediatrics (AAP) recommends not using picaridin on children younger than 2 months.

P-menthane 3,8-diol. This insect repellent is commonly known as lemon eucalyptus oil. When oil of lemon eucalyptus was tested against mosquitoes found in the U.S., it provided protection similar to repellents with low concentrations of DEET. It provides up to 2 hours of protection against mosquito bites. Do not apply more than twice per day, and do not use this product on children younger than 3 years.

Permethrin. This insecticide works on contact to kill mosquitoes. You spray it on clothing and other fabrics, such as mosquito netting and tent walls. Permethrin should not be applied directly to the skin. Several studies have found that using the combination of permethrin on clothing and DEET on the skin provides a much higher level of protection from mosquitoes than either permethrin or DEET alone.⁵

Soybean oil. Insect repellents that contain 2% soybean oil provide 1 to 4 hours of protection from mosquitoes when applied to the skin. Soybean oil is safe to use on infants and children.

Products that do not provide protection against bites for long periods of time

Citronella oil. Citronella as an insect repellent is not as safe or effective as products that contain DEET. Citronella applied to the skin provides between 30 minutes to 2 hours protection from mosquitoes. Some people develop skin rashes or itchiness when using citronella skin products because they must be reapplied often. Do not use citronella skin products on children younger than 2 years. Other kinds of citronella products, such as citronella candles and citronella wrist, neck, and ankle bands, do not prevent mosquito bites.

Other plant oils. Other plant oils, such as lavender and geranium, provide less than 30 minutes of protection against mosquitoes. Therefore, these products are not recommended.

Products sold as repellents that do not work well to prevent bites

There are other products advertised as mosquito repellents that do not effectively prevent mosquito bites. These include:

• Electronic (sometimes called ultrasonic) devices.
• Electrocuting devices, which are often called "bug zappers."
• Mosquito traps.
• Geranium house plants.
• Citronella candles.
• Taking thiamine (vitamin B1) supplements.
• Skin moisturizers that do not contain approved insect repellents.
• Wrist, ankle, and neck bands that contain repellents, such as DEET or citronella.

Citations

1. Fradin MS, Day JF (2002). Comparative efficacy of insect repellents against mosquito bites. New England Journal of Medicine, 347(1): 13–18.

2. Committee to Advise on Tropical Medicine and Travel (2005). Statement on personal protective measures to prevent arthropod bites. Canada Communicable Disease Report, 31: 1–20. Available online at http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/05vol31/asc-dcc-4/.

3. Centers for Disease Control and Prevention (2005). West Nile virus: Questions and answers-Insect repellent use and safety. Available online: http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm.

4. Abramowicz M (2005). Picaridin-A new insect repellent. Medical Letter on Drugs and Therapeutics, 47(1210): 46–47.

5. Fradin MS (1998). Mosquitoes and mosquito repellents: A clinician's guide. Annals of Internal Medicine, 128(11): 931–940.