Head Lice

What are head lice?

Head lice (Pediculus humanus capitis) are tiny insects that live in hair. Nits are the empty egg cases attached to hair that head lice hatch from. Head lice are a common problem, particularly in schools. They’re largely harmless, but can live in the hair for a long time if not treated and can be irritating and frustrating to deal with.

What are the symptoms?

The most common symptom is constant itching of the scalp. This may be accompanied by scratch marks or small red lesions resembling a rash on the head. There may also be a tickling feeling of something moving in the hair.

How are head lice diagnosed?

Head lice have three forms: egg (or nit), nymph, and adult. Nits are laid at the base of the hair shaft closest to the scalp. Nits are firmly attached to the hair, are oval shaped and very small. Nits appear yellow or white or sometimes as the same color as the hair of the infested person.

Nits hatch into nymphs in 8 to 9 days. Nymphs look like adult lice but are smaller. They mature into adults in 9 to 12 days. Adult lice are the size of a sesame seed, have six legs and are tan to grayish-white in color. They live for up to 30 days on a person’s head, but die within one or two days after falling off.

Infestations are diagnosed by finding adults, nymphs or viable eggs. A magnifying lens, good lighting and a fine toothed comb are useful. Head lice and nits are found on the scalp, particularly around and behind the ears and the near the neckline at the back of the head.

How can head lice be prevented?

Learn how to diagnose head lice and do regular inspections of children and family members. Check children when they return from overnight camps and school trips. During outbreaks, keep long hair tied back or braided to minimize hair-to-hair contact and discourage borrowing personal items like hats and hairbrushes.

How are head lice treated?

Head lice can be treated with an over-the-counter or prescription medication, usually as a shampoo. Treatment should be considered only for active infestations (adults, nymphs or viable nits are observed). Some steps to follow:

  1. Check household members and other close contacts and treat those with an active infestation.
  2. Treat all infested family members at the same time. Follow medication directions closely.
  3. A single treatment may not kill all the eggs. Retreatment usually should occur after seven to ten days to kill any lice hatched from surviving eggs before they produce new eggs.
  4. Repeated and thorough removal of lice and nits. Use a fine-toothed nit comb or fingers to remove all nits attached to hair shafts after treatment. Discard tissues or towel containing lice and nits. Clean combs and hair brushes by soaking in hot soapy water for twenty minutes or undiluted medicated shampoo for ten minutes. Continue to check for 2-3 weeks to be sure all lice and nits are gone.

In addition to medicated shampoos, other measures can be used but these are not required to treat a head lice infestation. Hats, scarves, pillow cases, bedding, clothing and towels used by the infested person can be machine washed and dried using hot water and hot air cycles.