Head lice

Expert reviewer, Dr Adrian Raby, General Practitioner
Next review due December 2023

Head lice are tiny insects that live on the hair of your scalp and neck. They’re not dangerous but can make your scalp itchy and uncomfortable. Nits are their empty egg cases. It’s good to treat head lice as soon as you can, to stop them spreading to other people.

A photo showing nits in hair

Nits are empty, white, egg cases of head lice. You may notice them stuck to your hairs.

About head lice

Head lice live on human hair and feed on blood from your scalp. This doesn’t hurt, but it can make your scalp itchy.

Adult head lice are around 3mm long – about the size of a sesame seed. If you have head lice, you’ll usually have up to around 30 lice living on your scalp. But if you have a very bad case, there could be up to 1,000 lice.

Female head lice lay eggs near your scalp. The eggs are attached to your hair with a glue-like substance. They take about a week to hatch, leaving behind empty, white egg cases called nits. You’re more likely to see the nits in your hair than the head lice themselves.

If you have nits, this doesn’t always mean you have live head lice too. After hatching, the nits can stay stuck to your hair, even once the lice have gone. You only know for sure that you have head lice if you find a living, moving louse on your scalp.

Anyone can get head lice, but they’re most common in children aged between four and 11. Most children with head lice are between the ages of seven and eight. Head lice are more common in girls and in children with long hair.

How do you get head lice?

You can only get head lice if your hair or head touches the hair or head of someone who already has them. Head lice can’t jump, fly or swim. They spread from person to person by crawling between hairs – it takes about 30 seconds for a louse to crawl from one person to another.

There’s no evidence that head lice prefer clean or dirty hair. You’re very unlikely to get them by sharing hats, combs or pillows – the lice can’t live for very long if they’re away from your head. Head lice can only live on humans – you can’t catch them from animals.

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Symptoms of head lice

Head lice don’t always cause any symptoms. So, you may not even know you have them.

Some people only know they have head lice when they spot the lice or nits in their hair.

  • Head lice are a brownish grey colour and can be difficult to see.
  • Nits are white and the size of a pinhead. You’re probably more likely to notice them on your hairs at the sides and back of your scalp.

If you have head lice, you may sometimes:

  • get an itchy scalp – but not everyone does
  • have small, itchy bumps around the edge of your scalp, especially at the back of your neck or behind your ears

Having head lice can make some people anxious. If you feel very itchy, you may find it hard to sleep. Try not to scratch, as this can lead to skin sores, which can get infected.

An itchy scalp doesn’t mean you definitely have head lice. This can be caused by lots of other things, such as eczema or dandruff. Some people even feel itchy when they hear they’ve been in contact with someone who has head lice.

You don’t need to treat head lice unless you find a living, moving louse on your scalp.

Checking for head lice

Head lice can be difficult to see just by looking at your child’s hair. You’re most likely to find them if you look at the hair around the back of their neck.

The best way to check for head lice is by using a special fine-toothed head-lice-detection comb. You can also use this comb to remove head lice. You can use detection combing when your hair is wet or dry. You don’t need to prepare much for dry combing. But wet combing may work better because the lice don’t move around when they’re wet.

You can buy a head-lice-detection comb from a pharmacy. Choose a comb made of good quality plastic, with teeth between 0.2 and 0.3mm apart. Don’t go for a metal comb because these may damage your hair or even pull hairs out. And don’t check for head lice with combs designed for nit and egg removal. The gaps on these are narrower, which can trap the lice so you don’t see them.

You should follow instructions on the product packaging or information leaflet that comes with your detection comb. You’ll usually need to take the following steps.

  • If you’re wet combing, wash your hair as normal first. Then put on plenty of conditioner (leaving this in until you’ve finished combing).
  • With both wet or dry combing, you should then smooth out and untangle your hair using a normal, wide-toothed comb.
  • Comb through sections of your hair using the detection comb, working your way through your whole head. Start at the roots by your scalp before drawing the comb all the way through your hair to the tips.
  • With wet combing, check the comb for lice after every stroke and remove them by rinsing or wiping the comb. For dry combing, you’ll need to look for live lice as you comb, and trap any using your thumb as you pull the comb out.
  • It can take up to 15 minutes to wet comb your hair and around five minutes for dry combing. But this will depend on your hair length and type.
  • You should check all members of your household (and any close contacts) for head lice with detection combing.

How do you get rid of head lice?

If you find a live head louse, you should aim to get treatment as soon as possible. Check everyone who lives in your household and treat anyone who has them at the same time. Children can still go to school – see our FAQ on whether or not to keep a child off school because they have head lice.

There are several treatments for head lice. You can either use a medicated lotion or spray or do wet combing (‘bug busting’).

Lotions and sprays

You can buy lots of different head lice treatments from a pharmacy without a prescription. These products contain an insecticide and you put them directly onto your hair. You should only use an insecticide treatment if you find live lice.

  • Dimeticone gels, lotions or sprays. Dimeticone is a physical insecticide – it kills the lice by coating them so they can’t breathe.
  • Isopropyl myristate and cyclomethicone solutions or sprays. These are also physical insecticides. They kill the lice by dissolving their outer wax coating.
  • Malathion. This is currently the only chemical insecticide recommended for use in the UK. It works by poisoning head lice.

If you’re using dimeticone products, stay away from fires and flames (including lit cigarettes) until you’ve washed the product out of your hair.

Products containing the insecticide permethrin are no longer recommended because head lice are becoming resistant to this insecticide.

You’ll need to put the insecticide on your hair and scalp and leave it for a certain amount of time. This can be as short as 15 minutes or as long as overnight depending on the product. So, read the product packaging first. You then need to wash the product out using normal shampoo. You’ll usually need to put the treatment on twice with seven days between the applications – this kills any new lice that may have hatched.

Some insecticides aren’t recommended for:

  • children under two years old
  • pregnant or breastfeeding women
  • people with eczema or asthma 

Instead, these people should use wet combing or dimeticone 4% lotion. Check with your pharmacist which products are best for you.

Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.

Wet combing or 'bug busting'

Wet combing involves removing lice by regularly combing wet hair with a plastic, fine-toothed head-lice-detection comb. If you’re using wet combing to remove head lice, you’ll need to do it every four days for two weeks. It’s important to keep wet combing your hair until you haven’t seen any full-grown lice for three consecutive sessions.

Wet combing is suitable for everyone. Some people prefer it to using an insecticide because it doesn’t involve any chemicals. It’s also relatively cheap because you can use the comb again and again. You can use one comb to treat all members of your family who have head lice. Wet combing should be done in four sessions spaced over two weeks – on days one, five, nine and 13. But it doesn’t always work as well as an insecticide. It can also take up a lot of time if several people in your family need to be treated.

Checking treatment has worked

Whichever treatment you use, you should check it’s worked by looking for lice with a detection comb. The advice about this varies. But it may be worth checking two or three days after you’ve finished the treatment and checking again after another seven days.

If you find any nits (egg cases), this doesn’t necessarily mean the treatment hasn’t worked. If you find live lice, the treatment may not have worked or you may have caught head lice again. You’ll need to repeat the same treatment, making sure you’re following the right instructions for the product.

Head lice can become resistant to the insecticide malathion. So, if malathion hasn’t worked for you, you should try either a physical insecticide or wet combing.

It’s important to check everyone in the household for head lice again at the same time – and treat them if you find any live lice.

Prevention of head lice

It’s hard to prevent head lice. You may want to teach your child not to share hairbrushes and combs – though lice don’t tend to spread this way. It may also help to keep any long hair tied up. The most important thing is to try and catch head lice as early as you can. Then you can treat them and stop them spreading to other people.

If your children are under the age of 12, it’s a good idea to check their hair regularly for head lice. You may want to do this once a week. It’s especially important to check if you know they’ve been in contact with other children with head lice.

You don’t need to wash the clothes or bedding of someone who’s had head lice. Head lice that fall off your head (onto hats or pillows) don’t live for very long.

Don’t use treatments for head lice unless you’ve found a living louse. You don’t need to keep children with head lice off school – see our FAQ on whether or not to keep a child off school because they have head lice.

Frequently asked questions about head lice

  • Use a special fine-toothed head-lice-detection comb to check for head lice, and to remove it. You can use detection combing when your hair is wet or dry. Wet combing may work better than dry combing because the lice don’t move around when they’re wet.

  • Adults can get head lice, but they’re most common in children aged between four and 11. If you have head lice, you’ll usually have up to around 30 lice living on your scalp. But, there could be up to 1,000 lice if you have a very bad case of lice.

  • Head lice live only on your scalp or behind your ears and at the back of your neck. They can’t live for very long anywhere else. But you can have other types of lice on your body, such as body lice or public lice.

    If you have itchy skin or think you’ve seen lice on your body, talk to a pharmacist or see your GP. If you think you have pubic lice, you can be treated at a sexual health clinic.

  • You don’t need to keep your child off school if they have head lice. But you should start treating them straightaway. And tell the parents of their close contacts, so they can check their child for head lice too.

    If your child has head lice, they’ll probably have had them for several weeks. Lots of other children at their school may also have head lice. So, keeping them away from school is unlikely to stop head lice being passed on.

  • Electronic combs aren’t recommended for treating head lice. This is because they’re expensive, and some experts worry they’re not safe if you don’t use them properly. Battery-operated combs may not reach your scalp very well. So, they don’t seem to be any better than a traditional louse-detection comb.

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Related information

    • Head lice. NICE Clinical Knowledge Summaries., last revised December 2016
    • The spotty book: notes on infectious diseases in schools and nurseries. Public Health England., last updated August 2020
    • Head lice. Patient., last edited August 2016
    • Pediculosis capitis. BMJ Best Practice., last reviewed October 2020
    • Head lice. British Association of Dermatologists., updated October 2020
    • Skin infections. NICE British National Formulary., last updated October 2020
    • Dimeticone. NICE British National Formulary., last updated October 2020
    • Lice. The MSD Manuals., last full review/revision May 2020
    • Pubic and body lice. Patient., last reviewed January 2017
  • Reviewed by Victoria Goldman, Freelancer Health Editor and Marcella McEvoy, Health Content Team, December 2020
    Expert reviewer, Dr Adrian Raby, General Practitioner
    Next review due December 2023