Facts about Head Lice

• Lice are genetically programmed to move from one head to another. They want to meet different lice (not their brothers and sisters on the same head) and breed with them. Lice cannot jump, hop, fly or swim, but have several ways of moving onto another person (Lancet 2003;361:99–100).
• The most common method is to grab onto another person’s hair during head-to-head contact. They grab the hair with one leg and then climb onto it.
• If they are in danger (if you agitate the hair), they may go to the end of the hair and drop off, hoping to land somewhere better.
• Head lice can live for 3 days away from the head, and eggs can survive for 5 days. Therefore, they could be spread by shared hats or helmets, combs, brushes, earphones or bedding. (Experts used to think this was unlikely but have now changed their minds.)

Who Gets Head Lice?

People of all ages can be infected by head lice. They are most common in children aged 4–11 (especially girls), probably because children have more head-to-head contact than adults. At this age, about 8% of children have head lice. Some people blame modern schooling, where young children are grouped around tables, instead of sitting at separate desks. Other people, such as grandparents, can then become infected. Outbreaks of head lice have occurred in residential care homes for the elderly, probably brought in by a child visitor.

Clean and dirty people are equally affected – head lice do not care. It is untrue that they prefer dirt. It is also untrue that washing gets rid of them. When the hair is washed, they crouch down close to the skin and stay still, to prevent themselves being washed out, so people who wash their hair every day are as likely to have lice as anyone else.

All social classes are affected.

Length of hair does not matter to lice, because they stay near the scalp. Short and long hair are equally likely to be infected. The only advantage of short hair is that it is easier to ‘wet-comb’ (see below) and very short hair makes it easier to spot the lice.

Type of hair can make a difference. In the UK, head lice are less common in Afro-Caribbean-type hair. The reason is probably that the lice in the UK are not well-adapted to clinging on to this type of hair. On the other hand, if a person of European descent, with straight hair, goes to Africa, he or she is unlikely to be infected by head lice there. The reason is that head lice in Africa are adapted to African hair and are not good at clinging on to straight hair.

More information can be found in our sections on how to tell if you have head lice and how to treat head lice. If your scalp is itching, but you don’t think you have head lice, see our pages on dandruff and itching.

First published on: embarrassingproblems.com
Reviewed and edited by: Dr Ahmed Kazmi
Last updated: October 2020