The Lowdown on Lice: SouthFlorida.com

Reports of head lice soar in winter, but parents will be happy to know that many cases are not the pesky parasitic insects at all, says Richard Pollack, Ph.D., instructor in immunology and infectious diseases at the Harvard School of Public Health in Boston.

"Lice are far less prevalent than people think," Pollack says.

In a study published in the August 2000 issue of the Pediatric Infectious Diseases Journal, Pollack reports that of 614 specimens submitted by parents, school officials and health care workers around the country, 41 percent were not lice or lice eggs, but other types of insects, pieces of dandruff or debris. Of the specimens that were lice-related, about half seemed to be signs of an older infestation not requiring further treatment.

Head lice are tiny insects that crawl in human hair and feed off the human scalp, creating the condition known as "pediculiasis" or "pediculosis." Not easily dislodged, head lice cling to hair shafts, usually moving from one person to another only through head-to-head contact. Head lice are not related to poor hygiene, have not been shown to carry disease and do not fly or jump.

Depending on skin sensitivity, itching may develop as an allergic reaction to saliva from each insect bite - but an itchy scalp doesn't necessarily mean lice.

Signs of Lice

Head lice are hard to detect because they are smaller than a sesame seed and tannish in color, but they appear darker in darker hair. Nits (lice eggs) - tiny, hard, grayish-white or yellowish specks firmly attached to the hair shaft - are often the first sign of infestation. Nits mature into adult lice in about two weeks and then can live up to 30 days on a human head. If a louse becomes separated from the scalp, it will die in under two days.

Who Gets Head Lice?

The U.S. Centers for Disease Control estimate that 6 million to 12 million people worldwide get head lice each year - and they are mostly preschool- and elementary-age children and their families. Accurate numbers aren't available because data isn't collected. "That's for good reason," Pollack says. "Head lice are not a disease, they're a minor nuisance at best."

Deborah Altschuler, president and founder of the National Pediculosis Association, objects to Pollack's dismissive attitude. While Pollack insists that head lice, though not pleasant, are not a public health hazard or cause for alarm or for keeping children out of school or child care, Altschuler disagrees.

Her organization advocates stringent "no nit" policies for schools, camps and child care, along with routine combing of children every day to screen for lice at home.

"Just like brushing your teeth every day," says Altschuler.

Which Treatment Is Best?

Experts disagree on the best method of eliminating a head lice infestation. Some recommend avoiding the use of chemical treatments altogether, especially on children. Physicians usually recommend the proper application of a pediculicidal (lice-killing) shampoo, lotion or cream - except for pregnant women, children under age 2, and people with ragweed or chrysanthemum allergies. Make sure that the product is specifically labeled for human use and contains one of the following insecticides:

pyrethrin, a natural extract of chrysanthemum (Rid, for example)
permethrin, pyrethrin's synthetic counterpart (as in Nix)
pyrethrum or other related chemical (e.g. various store brands).

Pediculicides don't kill eggs, so the first application is usually followed by another in a week to 10 days.
A safer alternative to chemical treatment is a daily combing with a metal-toothed lice comb until every louse and nit has been removed. While as effective as chemical treatments, it is more time-consuming. Combing is recommended in combination with insecticides as well.
Myths about head lice abound, especially on the Internet. Consult your child's physician or pediatrician before choosing any method of eradication.
Here are home remedies that persist, despite lack of scientific evidence confirming their usefulness:

Electronic or vibrating combs. These are not widely recommended by experts
Mayonnaise, mineral oil and olive oil. All three may smother lice when left on hair overnight but mayo can turn rancid and foster bacteria, and mineral oil may irritate the scalp.
Tea tree oil. Efficacy and safety factors, such as levels of skin-absorption, are not well established, whether used in shampoo or combined with other essential oils.

Have Lice Grown Resistant?

A recent study by Pollack and other Harvard researchers confirms the existence of some permethrin-resistant strains of lice. However, some treatment failure also has been attributed to misdiagnosis (that is, no active infestation or misidentification), incorrect application of pediculicide or reinfestation by a family member or classmate.

If live lice are seen in the hair after careful treatment with a permethrin-based shampoo, some experts recommend seeing a physician to determine whether treatment with prescription-only pediculicides, such as lindane or malathion, is warranted.

The Food and Drug Administration recently reapproved lindane for occasional use as a pediculicide, except for patients with seizure disorders, after finding that reported adverse reactions stemmed from repeated applications, inadvertent ingestion or leaving the product on too long. Malathion (found in Ovide) has been approved by the FDA for use on older children, although scalp absorption rates are as yet unknown.

The Pediculosis Association, the American Head Lice Information and Resource Center in Cambridge, Mass., and Mothers and Others in New York, however, warn parents against using either of these potent insecticides, labeling them unsafe for children and the environment.

The best defense against head lice is to stem their spread by reminding your children not to share headgear or hairbrushes - and not to put heads together, even in a gesture of friendship. Once lice have been detected, parents should follow these steps:

Wash bed linens in hot water and dry them in a dryer
Wash combs, brushes, and hair accessories in hot water daily
Treat only family members with signs of active infestation - no need for obsessive house cleaning, as only the scalp gets infested.

Head lice have coexisted with humans for thousands of years. Escaping a run-in with the pesky creatures is often a matter of luck.

Laurie A. Cavanaugh is a freelance writer and mother of three school-age living in Massachusetts.