Millions of parents will be rubbing insecticide onto their kids' heads - and maybe their own - as the new school year heralds a return of that nasty childhood nuisance, head lice.
Every year, 6 million to 12 million people in the United States get head lice, or pediculosis, a disease named for the culprit insect, Pediculus capitis.
Most are children under age 12 and their parents. Kids get pediculosis because they're in close contact and often share combs, hairbrushes, hats, scarves, earphones, and other objects that pass lice along.
Head lice are brownish-tan, wingless, and about an eighth of an inch long. Every four to six hours they make tiny pinprick-like holes in the scalp to feed on blood.
An itchy head is one sign of a lice infestation. Lice also may be visible in the hair or eyebrows. It's often easier to see the eggs, or nits. Each female lays 50 to 150 eggs, gluing them to hair shafts. Nits are white and about the size of a sesame seed on a bagel.
Head lice don't spread diseases and are usually only a nuisance. If kids scratch enough, the bites can become infected and may need antibiotic treatment.
Head lice get a lot of attention because they are unpleasant, and infested kids may be sent home from school. Many schools have a "No-Nit Policy," requiring kids to be nit-free before returning to school.
Shampoos containing pesticides are the quickest way to get rid of head lice.
Products like Rid, Nix, and Pronto Plus are sold without a prescription. Prescription products contain stronger and potentially toxic insecticides. Kwell, for instance, contains lindane, used to kill bugs on seeds. Ovide contains malathion, used in community mosquito-spraying programs.
Check on whether the product kills unhatched eggs as well as adult lice. Some come with fine-toothed combs and rinses to help remove the eggs.
Insecticides have been used for head lice for decades. So far as anyone knows, they seem safe when people follow the directions. However, there are health concerns about the prescription products' possible damaging effects on the brain and nerves.
Dr. Richard J. Pollack of the Harvard School of Public Health claims that the biggest danger from head lice is the use of insecticides and other materials to treat them.
California banned lindane for head lice in 2000. Several other countries have banned or restricted its use. The U.S. Centers for Disease Control and Prevention terms lindane "probably safe."
Like bugs in the outside world, head lice are developing resistance to some insecticides so repeat shampoos may be needed.
There are alternatives.
A study just reported in the British Medical Journal found that wet combing the hair after applying hair conditioner was four times more effective then insecticides. Peoples had to comb four days in a row, using the kind of nit combs sold with insecticide products or available separately in some stores. Flea combs for cats and dogs also may work.