Smarter Living: Family Health


photo: Dan Bergstrom

Mosquitoes are a nuisance, but in some areas they also transmit disease, such as West Nile virus and rarely other diseases here in the U.S. Ticks carry several diseases, the most common being Lyme disease. So protecting yourself against insect bites isn't just about comfort -- it can help keep you healthy.

The hazards from mosquito bites depend a lot on where you live and on the time of year. In many parts of the U.S., for most of the year, it’s very unlikely that local mosquitoes are infectious. However, when there are outbreaks of West Nile virus in your area, or if you live in areas where there have been outbreaks of Dengue fever (such as in Florida, South Texas, or Puerto Rico), or if you’re travelling abroad, then you need to take mosquitoes very seriously. Also, global warming may cause tropical diseases to spread to non-tropical areas, so insect repellants may be more important in the future.

Among the bug repellents available, it's important to know which actually work and which may pose health risks of their own. Here is a rundown of the options for protecting you and your family.


DEET is the most common ingredient found in insect repellents for one reason: It works. DEET provides an offensive odor that keeps mosquitos and ticks from landing and biting. It also discourages biting flies, fleas, no-see-ums (biting midges), sand flies, and several other biting insects. DEET is somewhat toxic to freshwater fish.

The EPA considers DEET to be only slightly toxic and not cancer-causing. In sensitive individuals, though, DEET can cause skin redness and irritation. And it has been linked to seizures in children: between 1960 and 1998, 46 cases of seizures were associated with DEET use in children. Given that millions of people use DEET, however, the agency estimates that DEET-associated seizures occur in just one per 100 million users.

DEET-containing products include: Cutter Adanced Insect Repellent, Off! Skintastic Insect Repellent, and Repel Sportsmen Formula Mosquito Repellent Wipes. (NRDC does not endorse these or other brands of insect repellents.)

How to Use

  • DEET should not be used on children under two months of age.
  • Apply DEET to children rather than letting them handle the product.
  • Avoid products that contain more than 30 percent DEET, since there is no increase in effectiveness, but there is an increase in toxicity
  • Avoid DEET-sunscreen combination products: Sunscreen must be frequently reapplied while repellents last much longer.
  • Avoid using DEET in a spray formulation, and especially avoid aerosol cans, since it’s hard to avoid inhaling the droplets.
  • Wash DEET off when coming indoors or at the end of the day.


A relative newcomer, picaridin was approved for use by the EPA in 2005, but has been available in Europe and Australia for longer. It works against mosquitoes and ticks as well as biting flies and chiggers.

Picaridin does not cause skin reactions. The EPA has not found picaridin to be a human carcinogen and considers it only slightly toxic when used on the skin. Typical usage of picaridin has no significant toxicity to children under the age of 12, according to a 2008 study.

Picaridin-containg products include: Cutter Advanced Insect Repellent, Sawyer Premium Insect Repellent, Avon Skin so Soft Bug Guard Plus Picaridin Pump Spray and Repel Sportsmen Formula Insect Repellent Pump Spray.

How to Use

Do not apply to children younger than two years of age.

Plant Oils

Plant oils and naturally derived pesticides are not as effective as DEET, but if there are no disease-carrying mosquitoes in your area, these may be a reasonable choice.

Just because these products are natural doesn’t mean they have no health effects. Concentrated plant oils can cause skin rashes and allergic reactions.

Oil of Lemon Eucalyptus has been used since 1948 to repel mosquitoes, biting flies, and gnats. A synthetic version, PMD, is aso available.

Oil of Citronella is marketed as a repellent for mosquitos, gnats, black flies and no see-ums. It is also used in insect-repelling candles.

Other Plant Oils: Soybean oil, lemongrass oil, and other plant oils are often found in repellents, but studies have found these are not very effective.

IR3535 is a synthetic biopesticide approved by EPA in 1999, although it’s been on European store shelves for decades. It repels mosquitos, deer ticks, and biting flies.

Plant Oil and biopesticide products include: Avon Skin So Soft products (I3535), Repel Lemon Eucalyptus Insect Repellent and California Baby Citronella Insect Repellent Spray.

How to Use

  • Plant oils can cause allergic reactions; test diluted oil on a small area of skin before applying more generally.
  • Oil of lemon eucalyptus should not be used on children under three years of age.

Insecticide-Treated Clothing

Several outdoor clotheswear manufacturers produce clothing and camping gear lines containing an insecticide in the fabric that can kill mosquitos, ticks, and other biting insects. Permethrin, the chemical in these products, won’t repel insects but will kill them on contact (for health and environmental information, see Pyrethroids).

The EPA found that permethrin is "likely to be carcinogenic to humans" but has approved it for use in clothing and many other insecticidal products, including household insect sprays and pet shampoos. Permethrin kills bugs by interfering with their nervous system, and there have been neurological effects reported in humans. Permethrin is also highly toxic to fish and bees, according to the EPA.

Permethrin-treated clothing can keep bugs away, but these products are not recommended for children. Toddlers and infants are more susceptible to neurological effects from chemicals because their bodies are still developing; and early repeated exposures to cancer-causing chemicals could increase an individual’s risk of developing cancer later in life.

How to Use

Avoid this clothing, unless you are travelling in a tropical country, or if you are spending time outdoors in an area with a lot of Lyme Disease. If you do need to use this clothing, remember to apply insect repellant to any exposed parts of your body that are not protected by clothing.

Bug-Repellent Fans

Recently available in stores, these small battery-powered fans clip to your belt or clothing and circulate a fine mist of metofluthrin, an insect-killing chemical similar to permethrin. This mist can easily be inhaled, which could be a significant health risk.

Metofluthrin is toxic to the nervous system in animal studies and also can harm the liver, according to the EPA. It also causes cancer in rodent studies and the EPA considers it “likely to be carcinogenic to humans.” The EPA approved the use of these fans based on the assumption that it would be used only occasionally, roughly 12 hours per day, 12 times per year, for 50 years.

How to Use

Avoid use of bug repellent fans.

Go Chemical-Free: Cover Up

Donning clothes or a mosquito net is a chemical-free and effective way to elude the bites of mosquitos, ticks, and other insects:

  • Wear long pants with the hem tucked inside socks.
  • Tuck shirts into waist bands.
  • Wear light colors to help you easily spot ticks and to discourage mosquitoes, which are drawn to dark colors
  • Make sure you have window screens in your home, and repair any tears or holes in the screens.

last revised 6/22/2011

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