It is strange, but people get so upset about a creature the size of a sesame seed that carries no diseases and usually causes no symptoms. Yet, many schools have draconian head lice prevention policies that keep perfectly healthy children home from school.

Parents needlessly waste time and energy trying to figure out where their child caught the lice. They unnecessarily spray their homes with insecticides and overuse these toxic chemicals on their children. It's this obsession with treatment that is the health menace, not the head lice themselves.

Head lice are tiny insects that live on human heads. They cannot jump or fly, so they are passed from one person to another by direct head-to-head contact. It's also possible - but less likely - to catch them by sharing a hairbrush, comb, hair accessories or a helmet or hat.

Lice don't care whether you have good or bad hygiene; washing your hair frequently does not prevent head lice.

Head lice cannot survive away from a human for more than two days. They need to feed on tiny amounts of blood regularly. Usually, there are fewer than 12 head lice on the scalp at any time.

Female lice lay their eggs - called nits - at the base of a hair shaft. The nits attach to the side of hair with a glue-like substance, and hatch seven to 10 days later. A female louse can start laying eggs about 10 days after she hatches, and can lay six eggs per day. The life span of lice is 30 days at the most.

Nits that are newly laid and likely to hatch are found very close to the scalp. Nits that are more than a quarter inch from the scalp have probably already hatched or are dead.

Both parents and health care professionals tend to overdiagnose head lice. It's easy to mistake dandruff for nits. Without a microscope, it's almost impossible to tell a hatched or dead nit from one that is going to hatch. Seeing living lice on the scalp is the best way to positively diagnose the problem.

If head lice have been positively identified, start with the least toxic treatment. Wash the hair and detangle it first, then sit down under a bright light and go through the hair from the scalp to the ends with a special fine-toothed comb designed for lice and nit removal.

This process can take an hour or more for children with thick, long hair. To make it more enjoyable, sing, tell stories or watch a favorite movie while you work.

Repeat this process daily until no lice are found for two weeks. Meanwhile, regularly vacuum furniture, car seats, stuffed animals and any fabric surfaces that your child's head has touched. Wash towels, sheets and pillowcases, then put them in a hot dryer for 30 minutes.

There is no need to use insecticide sprays in your home, and no need to treat pets.

Another nontoxic treatment is to cover the scalp with olive oil or mayonnaise and leave it on for at least two hours, or overnight. Wash it out with a shampoo for oily hair. Then, use your fine-toothed comb to remove the remaining nits and (hopefully) dead lice. This can be repeated every few days.

Over-the-counter lice treatments containing permethrin/pyrethrins (Rid® and Nix®) should only be used if the above measures are unsuccessful. Use them exactly as instructed, as they are toxic chemicals.

Other treatments such as lindane and malathion are even more toxic, and should be used only as a last resort, under the direction of a health care provider.

Experts at the Harvard School of Public Health believe the hysteria over head lice is unfounded. A child with a cold is much more likely to infect his classmates than a child with lice.

Kathryn B. Brown is a family nurse practitioner with a master's degree in nursing from OHSU. Is there a health topic you would like to read about? Send ideas to


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