Head lice

Expert reviewer Dr Adrian Raby, General Practitioner
Next review due July 2021

Head lice are tiny insects that live on hair on your scalp and neck. Nits are the empty egg shells from which head lice have hatched. Head lice can affect anyone but are most common in children under 12. Head lice aren’t a serious health problem, but they can be a nuisance, and make your scalp itchy and uncomfortable. It’s good to treat them as soon as you can, to stop them spreading to other people.

A photo showing nits in hair

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.

About head lice

Head lice live in human hair, and feed on the blood from your scalp. This doesn’t hurt, but it can make your scalp itchy. Adult head lice are around 3mm in length – about the size of a sesame seed.

With a typical case of head lice, you might have around 30 lice on your head. But it’s possible to have more than 1,000 lice if you have a severe infestation.

Female head lice lay eggs, which are attached to your hair with a glue-like substance. The eggs take about a week to hatch, leaving behind empty, white egg cases known as nits. These can be easier to see than the head lice themselves.

If you have nits, it doesn’t always mean that you have an ‘active’ head lice infestation (with live lice). After hatching, the nits can stay stuck to your hair, even once the lice have gone. You’re only said to have an active infestation 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. The peak age to get them is between seven and eight. They’re also more common in girls, and in children with long hair.

How do you get head lice?

You can only get head lice through direct head-to-head contact with a person who 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 have a preference for either clean or dirty hair. You’re extremely unlikely to get head lice by sharing hats, combs or pillows – head lice can’t live for very long once they’re removed 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

You may have no symptoms at all if you have head lice. Often, people don’t know they have them until they spot head lice or nits in their hair. Head lice are a grey-white to black colour, and can be difficult to spot. 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.

You may also start to get an itchy scalp if you have head lice – but not everyone does. As well as itching, you may have small, itchy bumps around the edge of your scalp, especially at the back of your neck. Try not to scratch, as you may develop skin sores, which can become infected.

Having these symptoms doesn’t always mean you have head lice. An itchy scalp can be caused by other conditions, such as eczema or dandruff. Some people feel itchy just by hearing that there are head lice within the school or community. There’s no need to start any treatment unless you find a living, moving louse on your scalp.

Checking for head lice

You might be able to see head lice in your child’s hair, especially if you look at the hair around the back of their neck and behind their ears. But the best way to check whether you or your child has head lice is by using a special fine-toothed head lice detection comb. You can also use this method to remove head lice if you prefer not to use other treatments. Detection combing can be done when your hair is wet or dry. Dry combing takes less preparation, but wet combing is more accurate because any lice will remain still 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, as these can be too harsh. And don’t use combs designed for nit and egg removal to check for head lice. 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. But you’ll usually need to take the following steps.

  • If you’re wet combing, you’ll need to wash your hair as normal, and then apply plenty of conditioner (leaving this in until you’ve finished combing).
  • Whether wet or dry combing, you should then smooth out and untangle your hair using a normal, wide-toothed comb.
  • Then, comb through sections of hair using the detection comb, working your way through the whole head. Start right at the roots before drawing the comb all the way through the hair to the tips.
  • With wet combing, check the comb for lice after each 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 5 minutes for dry combing, but this will depend on your hair length and type.
  • You should check all members of your household for head lice with detection combing.

How do you get rid of head lice?

If you’ve found a live head louse, you should aim to treat them as soon as possible. Check everyone who lives in the same household and treat anyone else who has them at the same time. There are a number of effective treatments available. You can either use a medicated lotion or spray or do wet combing (‘bug busting’).

Lotions and sprays

There are a number of treatments you can buy over-the-counter at your pharmacist to treat head lice. These are products containing an insecticide that you apply to your hair. You should only treat head lice with an insecticide treatment if you find live lice. Treatments include the following.

  • Dimeticone gels, lotions or sprays (eg Hedrin, NYDA and Linicin). Dimeticone is a physical insecticide – it kills the lice by coating them so that they can’t breathe.
  • Isopropyl myristate and cyclomethicone solutions or aerosol products (eg Full Marks and Vamousse). This is another type of physical insecticide that kills the lice by dissolving their outer wax coating.
  • Malathion (eg Derbac-M). This is currently the only chemical insecticide recommended for use in the UK. It works by poisoning the head lice.

Products containing the insecticide permethrin (eg Lyclear) are not currently recommended as there is evidence head lice are becoming resistant to it.

You’ll need to apply insecticides to your hair and scalp and leave it on for a certain amount of time, as directed in the product packaging. This can be as short as 15 minutes, or as long as overnight for some products. You then need to wash it out using shampoo. It’s usually recommended to apply the treatment twice, leaving seven days between the applications – this kills any new lice that may have hatched.

Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice. Some preparations aren’t recommended for children under two, for pregnant or breastfeeding women, or for people who have eczema or asthma. Wet combing or dimeticone 4% lotion (Hedrin Once) is usually recommended for these groups. Check with your pharmacist which products are most suitable for you.

Wet combing or 'bug busting'

This treatment involves removing lice by regularly combing wet hair with a plastic, fine-toothed comb, head lice detection comb. This is also the best method for detecting head lice – the technique for wet combing is discussed in the section above, Checking for head lice. If you’re using wet combing as a way to remove head lice, you’ll need to do this every four days for two weeks. It’s important that you keep wet combing your hair until you haven’t seen any full-grown lice for three consecutive sessions.

Some people prefer wet combing to insecticides, as it doesn’t involve using strong chemicals. You can also use this method if you have asthma or a skin condition, if you’re pregnant or breastfeeding, and at any age. It’s also relatively inexpensive as the combs are reusable; so one comb can be used to treat all members of your family that are affected. However, wet combing isn’t usually as effective as using an insecticide treatment and it can be time-consuming if you have many members of your family to treat.

Checking treatment has worked

Whatever treatment you use, you should check if it’s worked afterwards, by checking for lice with a detection comb. There’s different advice on when is the best time to do this. But it may be worth checking two or three days after you’ve completed the treatment, and repeating again after another seven days. If you find any nits (egg cases), it doesn’t necessarily mean that the treatment hasn’t worked. But if you find live lice, the treatment may not have been successful or you might have caught them again. You’ll need to repeat the same treatment, making sure that you are following the correct instructions for the product. Head lice can become resistant to the insecticide malathion, so it might be worth trying a different treatment if you’ve already tried this one. It’s important that you check everyone in the household for head lice again.

Prevention of head lice

It’s difficult to prevent head lice. You might want to teach your child not to share hairbrushes and combs – although it’s extremely unlikely for lice to spread in this way. It might help to keep long hair tied up. The most important thing though, is to try and catch head lice as early as you can, so you can treat them and stop them spreading to others.

If you have children under the age of 12, it’s a good idea to have a regular check of their hair for head lice or nits. You might want to do this routinely – for instance, once a week. But it’s especially important to check if you know they’ve been in contact with other children who have had head lice.

You don’t need to wash clothing or bedding of someone who’s had head lice. Head lice that fall off your head (onto hats or pillows) are likely to die soon after.

Don’t take treatments for head lice unless you’re sure you have them – this could just encourage lice to become resistant. It’s not necessary to keep children with head lice off school – see our FAQs for more information.

Frequently asked questions

  • No, head lice have adapted to live solely on the human scalp. You may have other types of lice on your body, but these won’t be head lice.

    Head lice and nits are almost always found only on your scalp, especially behind your ears, and at the back of your neck. They can’t survive for more than around a day or two once they’re removed from your head.

    There are two other types of lice that have adapted to live on the human body. These are body lice and pubic lice (‘crabs’). Body lice are different to head lice. They mainly live on bedding and clothing, not on people, and move on to your skin when they need to feed. You’re most likely to get body lice if you have dirty clothes, live in cramped, crowded conditions or share bedding. They’re most common in people who are homeless.

    Pubic lice most commonly live in your pubic hair but can spread to hair on other parts of your body, including in your armpits, eyebrows, chest, back and facial hair. Pubic lice are mostly sexually transmitted in adults, but they can be transmitted to children by close contact with parents.

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

  • No, it’s not necessary for a child to be kept off school if they have head lice. You should start treating your child as soon as possible after you’ve discovered they have head lice. But there’s no need for them to stay at home.

    If your child has head lice, it’s likely they will have had them for several weeks. Keeping them away from school is unlikely to reduce the chances of head lice being passed on – there’s no evidence that this helps.

    It’s not usually helpful for the school to alert other parents if a child has head lice. This doesn’t usually help with stopping head lice spreading. Instead, it just tends to make people anxious – and can lead to people using treatments when they don’t need to.

  • Electronic combs aren’t recommended for treating head lice.

    Experts don’t generally recommend using them because they’re expensive and may have safety risks associated with them if you use them incorrectly.

    Also, there isn’t enough consistent evidence to show that they work well or that they’re safe. Battery-operated combs may not reach to the scalp very well, and aren’t thought to offer any advantage over a traditional louse detection comb.

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Related information

    • Head lice. NICE Clinical Knowledge Summaries., last revised December 2016
    • Head lice. PatientPlus., last checked August 2016
    • Head lice. British Association of Dermatologists., updated May 2017
    • Pediculosis capitis. BMJ BestPractice., last revised June 2018
    • Dermatology - head lice. Oxford handbook of general practice. Oxford Medicine Online., published online April 2014
    • The spotty book: notes on infectious diseases in schools and nurseries. Public Health England, October 2017.
    • Lice (pediculosis). MSD Manual. www.msdmanuals, last full review/revision October 2016
    • Pubic and body lice. PatientPlus., last checked January 2017
  • Reviewed by Pippa Coulter, Freelance Health Editor, Bupa Health Content Team, July 2018.
    Expert reviewer Dr Adrian Raby, General Practitioner
    Next review due July 2021