June 15, 2012
By Claire McCarthy, M.D.
Boston Children's Hospital
Ah, summer. Time for relaxing, playing outside, going to the beach and bugs.
The itch from mosquito bites and the yuck factor of pulling out a tick can be really unpleasant, but that's not the only problem from these pests. They can carry illnesses, such as West Nile virus, Eastern Equine Encephalitis and Lyme disease are examples we see in the United States. In tropical parts of the world mosquitoes can carry dengue and malaria. All of these illnesses can be serious.
But many people are just as afraid of insect repellents as they are of bug bites! They worry that they are dangerous. Used properly, insect repellents can be safe. Here's a look at the options for keeping the bugs away.
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The Most Effective Repellents
- DEET (N,N-diethyl-m-toluamide or N,N-diethly-3-methyl-benzamide) If you're in an area with a lot of ticks or public health officials are warning about insect-borne illnesses, this is the repellent to use. It really gets the job done. The length of protection depends on the concentration of DEET: 10% will protect for a couple of hours; 20% for about twice as long. According to the American Academy of Pediatrics, it's safe to use concentrations of up to 30% with children. However, DEET is not recommended for infants less than 2 months old. Although it's very unlikely, DEET can cause neurologic side effects including seizures. (According to the Environmental Protection Agency, seizures occur in 1 in every 100 million users.)
- Lemon eucalyptus oil (or PMD, the man-made version) This repellent, which shouldn't be used on children under 3 years, works nearly as well as DEET against both mosquitoes and ticks.
- Picaridin This repellent works well against mosquitoes, but much less well against ticks.
- 2-undecanone (IBI-246) This chemical, which is found naturally in various plants, not only repels insects, but dogs and cats! It is good for about four hours against mosquitoes, two hours against ticks.
- IR3535(chemical name 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester) This has been used in Europe for many years; in the United States it is only available in Avon products. It works for about two hours against mosquitoes and ticks.
- Permethrin This insect repellent (which is also used for head lice and scabies) works well, but shouldn't be used on the skin just on clothing or mosquito netting.
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Less Effective Repellents
- Citronella, soybean or catnip oil These may help for a little while, but can't compete with DEET and the other repellents above.
- Avon Skin So Soft Tests show it only works for a few minutes.
- Citronella candles They might help a little, but are no substitute for bug spray.
- Wristbands soaked in repellents Studies show they protect for less than a minute.
- Devices, such as ultrasonic ones, that are supposed to keep insects away from your yard
- Bug zappers They are more likely to zap other insects than mosquitoes
- Garlic or vitamin B1 taken by mouth
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Tips for Using Repellents
- Don't use insect repellents on infants younger than 2 months old (you can put mosquito netting over the baby carrier).
- Don't let kids put a repellent on themselves!
- Apply a spray repellent outside so you don't breathe it in (or get it on household surfaces)
- Don't use repellents on cuts or irritated skin.
- Don't spray a repellent directly on the face. Instead, spray it on your hand and rub some on the face.
- Make sure kids wash their hands well before eating.
- Spray the repellent lightly (more is not necessarily better) on exposed skin and clothing.
- Don't reapply repellent unless absolutely necessary. (If you are outside for more than six hours or so, you may need to reapply it.) For this reason, it's not a good idea to buy the combination sunscreen and insect repellent products. Sunscreen should be reapplied frequently, but insect repellent should not.
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Prevention Is Key
Mosquitoes are most abundant between dusk and dawn.
- Try to plan inside activities for after dinner.
- If you are going for that evening walk or to see fireworks, wear lightweight long-sleeved tops and long pants sprayed with repellent.
- If you don't have screens in your windows, mosquito netting (available in camping stores and on the Internet) draped over the bed can make a big difference.
The most important way to keep mosquitoes away is to get rid of standing water. Mosquitoes lay their eggs there.
- Dump out any buckets or other collections of water in your yard (empty the kiddie pool at the end of the day, or cover it tightly) and do it again after a rain.
- When possible, scrub the container, as the eggs may stick to the sides even if you dump out the water.
To prevent getting Lyme or other infections carried by ticks, always check your children thoroughly for any ticks at the end of every day if they have been outside. Promptly remove any you find. To remove a tick, grasp it with a tweezer as close to the skin as possible and pull straight out.
It's difficult to imagine a summer without mosquito bites. But with a little effort, your child will spend less time scratching and more time having fun!
Claire McCarthy, M.D., is an assistant professor in pediatrics at Harvard Medical School, an attending physician at Children's Hospital of Boston, and medical director of the Martha Eliot Health Center, a neighborhood health service of Children's Hospital. She is a senior medical editor for Harvard Health Publications. [new]