Lice are small wingless insects. They have six legs with hook-like claws for grasping onto hairs. They feed on human blood. There are three types of lice.
- Head lice are common in children.
- Body lice are common in vagrants, live in clothing and only visit the skin to feed.
- Crab or pubic lice are found in the pubic hair area.
The short life of a head louse
- The louse begins as an egg, with a hard brown shell
- The egg hatches after 7–10 days, leaving behind the empty egg case, which appears white
- The baby louse takes10 days to grow into an adult, shedding its skin three times as it grows
- When the louse reaches adulthood, it is about the size of a sesame seed (about 3 mm long)
- The louse clings to hairs with its claws, and sucks blood from the scalp several times a day. If it is a female, it busies itself laying five eggs each night and attaching them to the base of hairs close to the scalp where they will be kept warm
- The louse keeps looking for any opportunity to get onto another head, by clambering across a ‘bridge’ of hair. It cannot jump
- After 30 days of being an adult, it dies
Written by: Dr Margaret Stearn
Edited by: Dr Margaret Stearn
Last updated: Friday, March 18th 2011
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In the UK, each month 20% of hairdressing salons see head lice in a client's hair
An estimated 5% of the UK population has head lice
Each year in the UK, the NHS and the general public together spend £29 million on head lice treatments
'Lousy', 'nitwit', 'nit-picking', 'nitty-gritty', 'go through something with a fine-tooth comb' - all these phrases come from lice
The average person with head lice has about 20 lice. During their 30-day life, 20 lice will lay 2652 eggs (Lancet 2003;361:99-100)
After mating, a female head louse keeps spare sperm in a special container in her body (spermatotheca), so that she does not have to bother with mating again, but can use the sperm she has kept (Lancet 2003;361:99-100)
Head lice are fairly speedy. They can move at 23 cm per minute (Lancet 2003;361:99-100)
Head lice have probably been annoying humans for at least 72 000 years (New Scientist 2003;23 Aug)