Head lice

Head lice are tiny wingless insects that are grey-brown in colour. They are the size of a pinhead when they hatch and 2-4mm long (the size of a sesame seed) when fully grown.

They cannot fly, jump or swim, but spread by clambering from head to head. It takes about 30 seconds for a louse to transfer from one scalp to another.

Head lice feed by biting and sucking blood through the scalp.

Although it is disputed, experts think that head lice take eight to ten days to mature into adult lice, after which they are capable of reproducing.

The female louse lays eggs in sacs (called nits), which are very small, dull in colour and well camouflaged. Nits are securely glued to hairs, where the warmth of the scalp will hatch them out in 7 to 10 days. Empty sacs are white and shiny and may be found further along the hair shaft as the hair grows out.

How common are head lice?

Anyone with hair can catch head lice, but children who have head-to-head contact, either at school or during play, are most commonly affected. Head lice are most common in children who are between four to eleven years of age. Head lice can affect anyone, whatever the length or condition of their hair (whether it is dirty or clean).

Head lice affect only humans and cannot be passed on to or caught from animals.

How are they treated?

Head lice and nits can be killed using lotions, or physically removed using the wet combing method (see Head lice - treatment for more information).

If you are worried about head lice or want more advice on how to treat them, consult your school nurse, health visitor, pharmacist or GP.