Patient information from BMJ

Head lice

Last published:Jan 04, 2022

Head lice are harmless, although they may make your head feel itchy. There are treatments available. Some children get head lice repeatedly.

What are head lice?

Head lice are small insects that live on people's scalps. They spread from one person to another, usually through head-to-head contact.

Having head lice is nothing to be ashamed of. It doesn't mean you don't keep yourself clean. Head lice can't tell the difference between clean hair and dirty hair. They are common, especially among children.

Sometimes head lice are called nits, even though the word 'nits' really means the shells of their eggs.

You can catch head lice if your hair touches the hair of someone who has them. But head lice move slowly. Your hair needs to be touching someone else's hair for about half a minute to catch lice. You're very unlikely to catch them from using someone else's hat, or pillow. Lice don't live for very long away from the scalp.

How do I know if I have head lice?

Head lice are not easy to see, so you may not notice them straight away.

Sometimes they make your head itch. But the only way to know that you have head lice is to find a live louse in your hair. Finding something that looks like a louse egg or nit does not mean that you have head lice.

A fully grown head louse is flat and about the size of a sesame seed. They don't have wings. Head lice are usually greyish-brown, but the colour can vary. You may find them when you comb your hair.

What treatments work?

There are two basic ways to try to get rid of head lice. You can either try to remove them by combing them out, or use a chemical treatment to kill them. Chemical treatments include insecticides, which poison the lice, or occlusive treatments, which kill them by covering them up.

Sometimes insecticides don't work because the lice have become resistant to the chemicals (this means that the chemicals will no longer kill all the lice). If this happens, you will have to try a different treatment.

Removing head lice by combing

This involves thoroughly combing wet hair with conditioner, using a comb with very fine teeth that can pick out lice. You can buy these combs in a pharmacy.

The idea is that by removing lice, you'll stop them laying eggs. After about two weeks, all the lice should have been removed. You need to carefully comb through your hair, or your child's hair, every two to three days for at least two weeks, to catch any newly hatched lice. You should keep carrying it out until you have found no lice for at least three combing sessions in a row.

Chemical treatments: insecticides

Lotions that poison head lice are called insecticides. Ask your doctor or pharmacist which treatment is best to try first where you live. Insecticides are not all suitable for young children.

You will probably need to apply the treatments at least twice, seven days apart, to be sure all the head lice have gone. Read the instructions carefully to see how to use the treatment and how long you need to leave it on the scalp.

Some people are concerned that some insecticides can cause health damage. But experts say there is nothing to show that the low doses used for head lice treatments are harmful. Some insecticides catch fire easily, so you need to take great care when using them.

Chemical treatments: occlusive treatments

Dimeticone is an example of an occlusive treatment. It is made from silicone. It kills the lice by coating them so water can't get in or out of their bodies. Because it is not an insecticide, head lice are less likely to be resistant to it. You need to repeat the treatment after seven days. Some people try using other substances to coat lice, for example, petroleum jelly or hair conditioners or lotions.

What will happen?

Head lice are rarely a serious problem, but they can be annoying. And if you don't get rid of them, they can spread to other people. You should check everyone in your house for lice, and treat them if necessary.

If you don't treat head lice, the problem will get worse as the lice breed. The scalp may get sore and itchy.

Head lice will not clear up on their own, so you shouldn't ignore them. It's easier to get rid of them if you treat them quickly.

Tell people you or your child has close contact with, even if you find this difficult. They can then check their hair or their children's hair. Head lice spread easily in families and schools. If you don't tell people, the lice will spread in your community and you or your child might catch them again.