Lice

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Lice are tiny parasites that live on human beings and feed on blood. They seldom cause serious medical problems, but they are both annoying and contagious.

Every four hours or so, a louse bites into a tiny blood vessel for a meal. You don't feel the initial bites, because lice inject an anesthetic. However, the bites later begin to itch, and your scratching can lead to infection.

Head lice (Pediculus humanus capitis) are about the size of a sesame seed and can be easily seen, although they hide quickly in response to light. Their eggs, called nits, are barely visible, whitish ovals cemented to hair shafts.

Head lice are extremely contagious, especially among schoolchildren. They afflict an estimated 6 to 12 million children in the United States. Twice as many girls as boys get head lice, not because of greater hair length, but because girls have more physical contact with one another and share more personal articles (hats, clothing, combs, headphones) that can transmit head lice. Head lice are rare among African Americans, possibly because the shafts of their hair have a shape that lice cannot grasp easily.

Pubic lice (Phthirius pubis) are yellow-gray insects found in the pubic region and transmitted by sexual contact. The size of a pinhead, they are slightly translucent and barely visible against light-colored skin.

They are also called crab lice, or crabs, because of their shape and the crablike claws with which they cling to hair. Eggs can barely be seen as tiny white particles glued so firmly to hair shafts that they are not removed by normal washing.

Body lice (Pediculus humanus corporis) are nearly identical in appearance to head lice but are more difficult to find.

When not feeding, they tend to hide in the seams of clothing and folds of bedding. Signs of their presence are scratch marks, hives, or small red pimples, usually on the shoulders, torso, or buttocks. If the lice are not treated, rashes or welts may develop.

Causes

Contrary to common belief, lice are not related to poor hygiene. In fact, head lice are thought to prefer clean hair to dirty hair. Lice live success-fully all over the world, wherever people gather in close proximity, as in schools.

Treatment

The goal of treatment is to remove all lice and nits. This usually requires repeated efforts, because a few adults may escape by hiding in clothing or bedding, and eggs are difficult to kill.

Conventional Medicine

To get rid of head lice, the most common treatment is to kill the adults with an insecticidal shampoo and to clear out the nits with a special fine-toothed comb. The safest and most effective preparation is permethrin cream rinse, available over the counter.

For best results, follow the directions exactly. Other family members should be treated; about 60 percent of infected children have relatives who carry lice. To avoid spreading the lice, infected children should be kept home from school until they are treated. Wash all clothing, towels, and bed linens in hot, soapy water, and dry in a hot dryer.

For those who prefer to avoid the use of insecticides, try a "combing only" technique. Wash the hair with ordinary shampoo and conditioner and leave wet. With a fine-toothed comb, stroke slowly outward from the roots through one lock of hair at a time. Lice will land on the back of the comb, get caught between the teeth, or fall off. Space at least 30 strokes over the head.

Repeat every three days. Because newborn lice do not lay eggs for the first week, all the lice should disappear after about two weeks of combing. Pubic lice can be treated with over-the-counter medications containing pyrethrins (natural insecticides).

To treat body lice, wash the entire body with soap and water. If this is not effective, you may have to use an insecticidal preparation, which usually kills all the lice.

Wash all clothing and bedding in hot water and dry in a hot dryer. Store clothes for two weeks in plastic bags or place them in dry heat of 140°F for three to five days.

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