August 17, 2009
By Claire McCarthy, M.D.
Boston Children's Hospital
Ah, summer. Time for relaxing, playing outside, going to the beach — and mosquitoes.
The itchiness from the bites can be maddening, but that's not the only problem with mosquitoes. These tiny, annoying insects can carry illnesses. West Nile Virus and Eastern Equine Encephalitis are two 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 mosquito bites! They worry that they are dangerous. Used properly, insect repellents are quite 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) – This is the most commonly used repellent — and the most effective. Both the Centers for Disease Control (CDC) and the American Academy of Pediatrics (AAP) recommend DEET. In 2003, the AAP said that it was safe to use products with up to 30% DEET. Make sure you read the label. The stronger the concentration of DEET in a product, the longer it will protect you. Concentrations around 5% will protect for an hour or so, while those closer to 30% can protect for several hours.
- Picaridin – This repellent, which is also applied to your skin, is less widely available, but is also effective.
- Lemon eucalyptus oil – This repellent, which shouldn't be used on children under age 3, comes from a plant. It is about as effective as low concentrations of DEET. It is found in sprays and lotions.
- 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.
- 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. (Only apply once a week for a few hours when using it for head lice or scabies.)
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Less Effective Repellents
- Those made from botanicals – 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 chemicals
- 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, so 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. And 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. That is where mosquitoes lay their eggs. 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.
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]
