Head Lice: How They Spread, How to Find Them and How to Treat Them

Head lice are tiny insects that live on people's heads and feed on human blood. Adults are about the size of a sesame seed; their eggs, called nits, are even smaller — about the size of a flake of dandruff. Lice and nits are found on or near the scalp, most often at the neckline and behind the ears.

Head lice are one of three kinds of lice that live on people; the others are body lice and pubic lice. Each is different, and having one kind doesn't mean you'll get another.

How they spread

• Lice crawl; they can't hop or fly.
• They spread through close, head-to-head contact, and only rarely through shared items such as hats or hairbrushes.
• Hygiene and cleanliness have nothing to do with it.
• Head lice don't spread disease.

Children aged 3 to 11 and their families get head lice most often, because young children touch heads while playing.

Symptoms

• a tickling feeling in the hair;
• frequent itching, an allergic reaction to the bites;
• sores from scratching, which can become infected;
• trouble sleeping, since lice are most active in the dark.

Diagnosis

Head lice are usually diagnosed by seeing a louse or nit. Because they're tiny and quick, a magnifying lens and a fine-toothed comb help.

Treatment

Over-the-counter and prescription shampoos, creams and lotions treat head lice. Ask a pharmacist or provider if you're unsure which to use, and check with your provider first if you're pregnant or nursing or treating a young child.

1. Apply the product exactly as directed, only to the scalp and the hair attached to it — not other body hair.
2. Use one product at a time, unless your provider says otherwise.
3. Follow the instructions on how long to leave it on and how to rinse it out.
4. After rinsing, use a fine-toothed nit comb to remove dead lice and nits.
5. Check and comb every 2–3 days for 2–3 weeks to be sure they're all gone.
6. Check everyone in the household and other close contacts, and treat them if needed.

If an over-the-counter product doesn't work, ask your provider about a prescription treatment.

Preventing spread

If someone has lice, along with treatment:

• wash clothes, bedding and towels in hot water and dry them on the hot cycle;
• soak combs and brushes in hot water for 5–10 minutes;
• vacuum floors and furniture, especially where the person sat or lay;
• seal unwashable items in a plastic bag for two weeks.

To keep children from spreading lice, teach them to avoid head-to-head contact during play and not to share things worn on the head — hats, headphones, hair ties, helmets. Check your school's or day care's policy; a child may need to stay home until fully treated.

Skip the home remedies. There's no clear scientific evidence that mayonnaise, olive oil or similar substances smother lice, and never use kerosene or gasoline — they are dangerous and flammable.

Sources

Based on the MedlinePlus health topic "Head Lice," National Library of Medicine, with a summary from the Centers for Disease Control and Prevention; a work of the United States government in the public domain.