Block That Bite
For: Wellness Made Easy, July 2003
Why do bugs bite people? To get a square meal. Researchers are learning more about why mosquitoes are more attracted to some people than to others, and why some pests prefer certain body parts. It all has to do with chemicals we secrete—chemicals that mosquitoes, ticks, and similar creatures love—as well as the temperature and smell of human skin. One day we may be able to swallow a pill that will repel insects and ticks.
Meanwhile, it pays to fight off biting insects with the means currently at hand. Deer ticks can carry the corkscrew-shaped bacteria that cause Lyme disease. Dog ticks carry the microorganisms for Rocky Mountain spotted fever. Most North American mosquitoes (except for a few species in California and the southwest) cannot carry malaria or yellow fever, but the latest mosquito-borne illness is a form of encephalitis caused by the West Nile virus. It has led to seven deaths in and around New York City; 62 cases of the disease were reported in 1999.
On a less threatening level, mosquitoes, biting flies, and no-see-ums can spoil picnics, tennis matches, and other outdoor fun, leaving everybody with itchy welts. But there’s plenty you can do.
In choosing a repellent or insecticide, you should weigh various factors. For instance, going on a camping or fishing trip in the wilderness may require stronger, longer-lasting measures than does sitting on the back porch in the evening. Are you in an area where Lyme disease is prevalent? Then you need to take extra precautions against ticks. How will you be dressed—in shorts and a T-shirt, or fully covered?
Never underestimate the usefulness of clothing in protecting you from insects, as well as from the sun. If you’re walking in the woods, keep ticks off your skin by wearing long sleeves and long pants and tucking trouser cuffs into your socks or boots. If you wear white or tan, rather than black, you have a better chance of seeing a tick if it crawls onto you. And you can use some of the products below to tick-proof clothing, rather than applying them to your skin.
Products with deet
There are dozens of products containing deet (short for N,N-diethyltoluamide). You can get lotions, solutions, creams, sticks, and sprays. Deet is a repellent, not an insecticide. That is, it keeps bugs from biting but does not kill them. It was developed for soldiers, and has been in use worldwide since 1953. It works well and has an excellent safety record when used properly, as follows:
• Read and follow the directions carefully.
• Don’t use deet on cuts, wounds, or abraded skin. Avoid getting the product in your eyes. If using a spray, apply it to your hands and then rub it on your face, rather than spraying your face directly.
• For ordinary purposes, don’t use a product on your skin that contains more than 30% deet. Concentrations of 10 to 30% are adequate for adults engaged in backyard activities. Use lower concentrations for children (see below).
• Apply thoroughly, but avoid frequent reapplication.
• Apply only on exposed skin, not under clothing.
• Deet is also effective when applied to clothing. It is safe on cotton, wool, and nylon, but can damage acetate, plastic, spandex, vinyl, and other synthetics. Close knits, such as jeans, don’t need deet: the clothing offers enough protection. But loosely woven knits do need to be treated.
• When you go back indoors, wash off the repellent.
• If you are going to the tropics or plan to be outdoors in infested areas for several days and will be wearing repellent for long periods, one good product to try is Ultrathon, a 33% concentration of deet in a controlled-release formulation that lasts for 12 hours. Another good choice is Sawyer Controlled Release lotion, which enhances protection without a high dose of deet (20%). With these products, you need to reapply less often. Look for them on the Internet or in travel-merchandise catalogues; some drugstores may also stock them. If you cannot find these products, don’t buy anything that is more than 50% deet. The higher the concentration over 50%, the greater the risk of skin problems.
Something even better on clothes
Permethrin kills ticks, as well as mosquitoes, black flies, and other insects. A repellent and an insecticide, it must not be applied to your skin. Applied to clothing, it is the best shield against ticks, and it lasts through several washings. You can also use it on bedding, particularly mosquito netting, when camping out. Hardware and garden-supply stores sell permethrin products, such as Permanone and Duranon.
As with deet products, read and follow the directions carefully. Launder fabrics and then apply permethrin. Spray applications are effective for up to 14 days of exposure, or through five washings. Clothes dipped in permethrin will repel/kill insects for even longer.
Plant-based products
Products with citronella, a natural
oil from tropical grasses, provide limited protection from mosquitoes,
though the strong smell of citronella
puts some people off. Avon Skin-So-Soft comes in formulations with and
without citronella, and either way can repel mosquitoes for up to an
hour, though no one is sure how it works.
None of the plant-based products will work against ticks, nor do they
claim to. Though popular, these products are of limited usefulness, especially
since protection is not long-lasting.
Final thought: Electric bug zappers, ultrasonic gadgets, and incense, often marketed for protection against biting bugs, have never been shown to be effective. You should not rely on them.
Protecting kids The EPA no longer allows any deet products to be labeled as specifically formulated for children. That’s not because repellents with deet are unsafe for kids. Used as directed, they are safe. But how—and how often—a repellent is applied is more important than the concentration. Here’s what to keep in mind:
|
UC Berkeley Wellness Letter, June 2001