Head lice are insects that live on the scalp and neck. Although head lice may be embarrassing and sometimes uncomfortable, they don't usually cause illness. However, they won't clear up on their own and you need to treat them promptly.
About head lice
Symptoms of head lice
Causes of head lice
Diagnosis of head lice
Treatment of head lice
Prevention of head lice

About head lice

Head lice are wingless insects. They are grey or brown, have six legs and are about 1 to 3mm in length when fully grown (the size of a sesame seed). Female head lice lay eggs that are smaller than a pinhead and these attach to your hair close to the scalp. The eggs hatch about seven to 10 days later. Young lice are called nymphs – it takes about 10 days for them to become adults and capable of laying new eggs.
When lice hatch they leave empty shells called nits attached to the hair. Nits are white and you may mistake them for flakes of dry skin. Unlike dandruff, nits stick to the hair and you won’t be able to remove them with normal shampooing.

Symptoms of head lice

For many people, head lice cause no symptoms. They can give you an itchy scalp. You may find this is worse behind your ears or on the back of your neck.
If you scratch a lot, the skin can become broken and infections may develop.
Other signs of head lice infection include nits stuck to the hairs as they grow out.
If you spot nits or droppings then you need to make a further investigation. Head lice aren’t always to blame your symptoms. For example, an itching scalp can be due to other causes such as eczema and dandruff. Eczema may be triggered by repeated treatments with insecticides.
It’s also possible to develop ‘louse phobia’, where people feel they have an infestation because they know of others who have been affected. For this reason it’s essential to have a confirmed diagnosis before starting treatment.

Causes of head lice

Anyone can get head lice, but they are most common in children aged between four and 11. This may be because of their close contact with each other at school. Girls seem to be more likely to get them than boys.
You can only get head lice through head to head contact. They cannot hop, fly or swim. Head lice can only live for a short time away from the scalp and those found away from the head are usually dying.
Head lice can be found in all types and lengths of hair – having head lice is not a sign that your hair is dirty. They are just as often found living in clean hair.

Diagnosis of head lice

Head lice are hard to spot on the hair but you can remove and then identify them by combing them out. This is called detection combing. You do this by combing the hair in sections using a special fine-toothed comb, available from pharmacies.
You will probably find it easier to comb the hair if it is wet and you apply a few teaspoons of olive oil or hair conditioner (rinse this off afterwards) as head lice can move rapidly in dry hair. It's important to comb the entire length of the hair from root to tip. After each stroke, check the comb for lice. You can also comb hair over a piece of paper, a white tissue or a bowl of water, which you can then check for lice. It will probably take you about 10 to 15 minutes to comb a head.
If you're in doubt about what you have found, you can tape a suspected louse to a piece of paper and ask a health professional (a school nurse or pharmacist, for example) for confirmation. They will be able to advise you on suitable treatments.
Infestation is only confirmed if you find a live head louse.

Treatment of head lice

If you do confirm head lice infestation, there are a number of treatments available including:

  • insecticides
  • wet combing ("bug-busting")
  • non-insecticide products



Some types of insecticides are available over the counter, such as:

  • malathion (eg Derbac M)
  • phenothrin (eg Full Marks liquid)

Another type, permethrin (Lyclear Crème Rinse) was available for treating head lice. It’s now only recommended for body and pubic lice.
Insecticides for treating lice are available as lotions, liquids or shampoos. You will need at least two applications of the product, seven days apart, so that the lice that hatch from the eggs after the first treatment are killed.  A maximum of three treatments should be used in any one course.
The products are either alcohol-based or water-based and there does not seem to be any difference in effectiveness between the two. Alcohol-based insecticides are not suitable for everyone, particularly if you have eczema or asthma, so it is usually recommended that you use water-based products. These are also recommended for young children.
If you are pregnant or breastfeeding you should try to use wet combing instead, but you can use malathion preparations if you need to. Check with your pharmacist, GP or health visitor before using any insecticides. Don’t use insecticides to treat children under the age of two – use wet combing if possible.
Always follow the instructions carefully. Usually the insecticide lotion should be rubbed onto your scalp and hair (or your child’s) and left for at least 12 hours before you wash it out. Shampoos and foams aren’t recommended because they do not remain in contact with the lice long enough to kill them.
Insecticides can cause side-effects such as scalp irritation. Only use them if you’re sure there is a head lice infestation.

Wet combing or "bug busting"

This is a method of removing lice with the regular use of a fine-toothed comb (teeth must be 0.2 to 0.3mm apart). You need to spend approximately 20 to 30 minutes combing through the entire head of hair every three days for at least two weeks. It is important that you keep doing this until there have been three consecutive sessions without seeing any lice.
You can get a "bug-busting" kit on prescription, from a pharmacy or from the charity Community Hygiene Concern. The kit contains four specially designed combs and detailed advice.
Wet combing doesn't involve strong chemicals, and lice can’t become resistant to it. It can also be used for routinely checking the hair for infection. Research shows that in general it’s probably less effective than insecticides, but you may prefer wet combing if you want to avoid chemical products.

Non-insecticide products

There are several other products available to treat head lice. These products don’t contain chemicals and kill the lice by coating their surfaces.
Dimethicone (Hedrin)
This coats the surface of the lice. It’s colourless, has no smell and has a slightly oily consistency. You need to wet all of the hair with the lotion and leave it to dry naturally before washing out eight hours later
As with insecticides, you will need to repeat the treatment after seven days to kill any new lice that have hatched. Dimethicone doesn’t irritate the scalp and lice can’t become resistant to it.
Full Marks Solution
This is a relatively new product and there is currently no evidence for its effectiveness. It’s an oily liquid that has to be combed through the hair and washed off after 10 minutes. Full Marks solution soaks into the louse’s coat and appears to block its breathing tubes. It’s too early to say whether it is quite as good as insecticides but may be another option for parents who don’t want to use insecticides.
Other treatments are available that contain essential oils (including tea tree), herbal extracts or homeopathic tinctures. There is no scientific evidence to show that these work. It’s important to remember that even though these products may be called ‘natural’, they can still be harmful.

After treatment

Whichever treatment you use, a follow-up check using a nit comb should be carried out a few days after the course of treatment.
If you do find any eggs, it doesn't necessarily mean that the treatment has failed – the lice may have been killed and you could just be seeing empty egg cases. If you do find a live adult louse, it may be because you have been re-infested.
Treatment does sometimes fail, often because insecticides aren’t used properly. Lice can also become resistant to one or more insecticides. If this happens, you may need to use a different insecticide, one of the non-insecticide products, or try wet combing. A school nurse, pharmacist or GP can advise you on the best insecticide to use depending on patterns of resistance in your area.

Prevention of head lice

The best way to prevent head lice spreading is to check your whole family's heads regularly and treat them as soon as live lice are found.
It's important to check your own hair and your children’s hair if you have been in contact with someone with confirmed head lice, so that all cases can be treated simultaneously.
To minimise head lice spreading to other people, and to prevent you or your child getting them again after treatment, it‘s essential to tell everyone you or your child has been in contact with about their possible exposure. They can then be checked and treated if necessary as soon as possible. This includes schools, nurseries and other family members such as grandparents. However, you don’t need to keep your child off school as he or she is likely to have had head lice for several weeks before you find them.
Studies have shown head lice repellents aren’t effective.
There is no need to treat bed linen, towels or hats with insecticides. Head lice don’t survive away from the scalp and can only pass from person to person by head to head contact. Pets don’t spread human head lice.


Do head lice bite?
Can head lice spread to my body?
Are electronic combs good at treating head lice?

Do head lice bite?

Yes, they feed by biting your skin and sucking blood from your scalp. 


Head lice feed on blood about five times a day, mixing it with their saliva, but the biting doesn’t hurt and many infestations cause no symptoms at all. Sometimes the biting can cause itching.  Some people have an allergic reaction to the bites and this can make the itching worse.

Can head lice spread to my body?

No, it’s very unusual for head lice to move onto your body or other areas of hair such as your eyelashes or eyebrows.


Adult head lice can’t survive for very long if they are removed from your head and so wouldn’t be able to live on another part of your body. There is a different type of louse, called the body louse that looks the same as a head louse but lives mainly in clothing and bedding, moving on to your skin when they want to feed.
You will usually only get body lice if you have dirty clothes or if you don’t change them very often. A third type of louse, also known as ‘crabs’ live in pubic hair, but can spread to other hair. It is mostly sexually transmitted.
If you’re concerned then you should see your GP for advice.

Are electronic combs good at treating head lice?

Electronic combs aren’t recommended because they can be expensive and can’t completely get rid of head lice.


Electronic combs can kill live head lice by electrocuting them. But they can’t kill the eggs so can’t be used to completely get rid of head lice. If you do wish to use an electronic comb then you should use it when your hair is clean and dry and follow the instructions that come with it carefully.

Further information



  • Head lice. Clinical Knowledge Summaries. www.cks.nhs.uk, accessed  28 October 2009
  • Roberts, R. Head lice. N Engl J Med 2002 346:1645–50
  • The prevention, identification and management of head lice infection in the community. Health Protection Agency, 2007. www.hpa.org.uk
  • Head Lice: Evidence based guidelines based on the Stafford report. Public Health Medicine Environmental Group, 2008. www.phmeg.org.uk
  • Head Lice: a report for Consultants in Communicable Disease Control (CCDCs). Public Health Medicine Environmental Group.www.phmeg.org.uk, accessed 28 October 2009
  • Simon C, Everitt H and Kendrick T. Oxford handbook of general practice. 2nd ed. Oxford: Oxford University Press, 2006: 675
  • Update on treatments for head lice. DBT 2009; 47:50–2. doi:10.1136/dtb.2009.04.0014
  • Parasitical preparations. Joint Formulary Committee. British National Formulary.  www.bnf.org, accessed 28 October 2009
  • Does dimeticone clear head lice? DTB 2007; 45:52–5. doi:10.1136/dtb.2007.45752
  • Nash B. Treating head lice. BMJ, 2003; 326(7401): 1256. doi:10.1136/bmj.326.7401.1256
  • Drug Safety Update. MHRA. www.mhra.gov.uk, accessed 1 November 2009
  • Head lice: factsheet for schools. Health Protection Agency. www.hpa.org.uk, accessed 28 October 2009


Related topics

  • Head lice
  • Insect bites and stings

Related articles

Published by Bupa's Health Information Team, December 2011. This factsheet is for people who have measles, or who would like information about it. Measles is a contagious illness...
Short-sightedness is a vision problem which means that people can’t focus on distant objects, making them look blurred.   The medical term for short-sightedness is...