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 your scalp. They take six to 14 days to become fully grown, 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 seven to 10 days.
Empty sacs are white and shiny and may be found further along the hair shaft as the hair grows out.
Who is affected?
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 not fussy about hair length or condition (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?
Headlice and nits can be killed using lotions or physically removed using the wet combing method (see Treatment for more information).
If you are worried about head lice or feel you need more advice on how to cope, consult your school nurse, health visitor, pharmacist or GP.
