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Head lice

Key points

  • Head lice are small, wingless insects that live on the hair of your head and neck.
  • They spread by direct head-to-head contact, and can’t jump, fly or swim.
  • They cause itching but are not usually a serious problem.
  • Finding a live louse on your head is the only way to confirm you have head lice.

Featured FAQ

Should a child with head lice be kept off school?

If your child has head lice he or she can still attend school. If your child has head lice, he or she will have had them for several weeks so keeping them away from school is unlikely to reduce the chances of head lice being passed on. Most schools will always have some children with head lice at any one time.

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Head lice are small insects that live on the hair of your scalp and neck. They aren’t a serious health problem and rarely cause anything more than an itchy scalp. However, they can be embarrassing and uncomfortable, and should to be treated promptly.

About head lice

Head lice (also known as Pediculus capitis) are small, wingless insects with six legs. They are greyish-white to black in colour and the legs have hook-like claws that hold onto your hair. Adult head lice are around 2mm to 4mm in length – about the size of a sesame seed.

Female head lice lay eggs, which are attached to your hair shaft. The eggs take about a week to hatch, after which an empty egg case often remains. These are known as a nits. Young lice are called nymphs – they take about six to 10 days to mature to adults and feed on blood from your scalp to survive. Adult lice can live for up to 30 days. A typical head lice infection is up to 10 live lice per head, but it can be up to thousands.

Head lice can be found anywhere on your scalp. They are most commonly found behind your ears and at the back of your neck. They can only live on human hair – you can’t catch head lice from animals. If you have nits, it doesn’t always mean that you have head lice. After hatching, the nits can stay stuck to your hair shaft. You only have head lice for sure, if you find a living, moving louse on your scalp.

Symptoms of head lice

You may have no symptoms at all if you have head lice. Itching can start if you become sensitive to louse saliva or faeces. This usually takes four to six weeks, but can it be up to three months before you have any itching. You might get a tickling feeling, or the feeling of something moving in your hair.

As well as itching, you may develop a rash behind your ears and at the back of your neck – this is caused by a reaction to the louse saliva or faeces. If you scratch a lot, you may develop skin sores, which can become infected. You might see nits stuck to your hair shafts.
Having these symptoms doesn’t always mean you have head lice. For example, an itchy scalp can be caused by other conditions, such as eczema or dandruff. Some people develop itching just by hearing that there are head lice within the school or community. It’s important that you don’t start any treatment until you have been diagnosed with head lice, or you find a living, moving louse on your scalp.

Causes of head lice

Anyone can get head lice, but they are most common in children aged between four and 11 – the peak age is between seven and eight.

Other risk factors for head lice include:

  • being a girl
  • living in a household with four or more children
  • having long hair

You can only get head lice through direct head-to-head contact with a person that has them. Head lice can’t jump, hop or swim. There is 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 – a louse’s lifespan is very short once it’s removed from your head.

Diagnosis of head lice

You can only be sure you have head lice if you can find a living louse on your scalp. They can be hard to spot, but you can comb your hair using a fine-toothed comb to find and remove them. This is called detection combing and it can be done when your hair is wet or dry. Applying conditioner to wet hair can be helpful because the lice can’t move as quickly so they are easier to see on the comb. After each stroke, check the comb for lice. It can take between five and 15 minutes to wet comb your hair, depending on how long and curly it is.

If you do dry detection combing and spot a louse on the comb, place your thumb on it before pulling the comb through and out of your hair. This will stop any lice being flicked off the comb. Check all members of your household with detection combing so you know who will need treatment.

Treatment of head lice

Head lice can be uncomfortable and embarrassing, but are not a serious health problem. There are a number of effective treatments available. You can either use an insecticide treatment or do wet combing (‘bug-busting’).

Insecticide treatments

There are a number of insecticide treatments available over-the-counter at your pharmacist to treat head lice. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice. You should only treat head lice with an insecticide treatment if you find live lice. Apply the treatment twice, leaving seven days between the applications – this kills any new lice that may have hatched. All members of your household that have head lice should be treated at the same time.

Insecticides are usually well tolerated. Your skin might become slightly irritated from the treatment, but this is usually mild and clears up on its own. Treatments are likely to be successful when you apply the treatment correctly and all affected members of your family are treated on the same day.

Dimeticone 4% lotion (Hedrin)
This is a physical insecticide, which means that it doesn’t contain chemicals and kills the lice by coating them and blocking their breathing tubes. You should apply dimeticone to your hair and scalp, and leave it on for eight hours, or overnight. You then need to wash it out using shampoo. The lotion is suitable for all ages, however, check with your GP first if you need to use it on a child younger than six months. It can be used if you have asthma or skin conditions, such as eczema.

Dimeticone 92% spray (NYDA)
This is also a physical insecticide. This treatment involves applying the spray and then combing your hair with a fine-toothed comb 30 minutes later. The treatment is then left on your hair and scalp for eight hours, or overnight, and then washed out using shampoo. It isn’t suitable for children younger than two.

Malathion (eg Derbac-M, Prioderm)
This is a chemical insecticide. You apply it to your hair and scalp, and leave it for 12 hours or overnight, then wash it out using shampoo. Some preparations are not recommended for children who have severe eczema or asthma. Check with your GP if you wish to use it on children under six months, as you may need a prescription.

Wet combing or 'bug busting'

This treatment involves removing lice by regularly combing wet hair with a plastic, fine-toothed comb (‘Bug Buster’ comb). You need to do this every four days for a minimum of two weeks, spending around 30 minutes each time combing through your entire head. It’s important that you keep wet combing your hair until you haven’t seen any full-grown lice for three consecutive sessions. You might find wet combing easier to do by applying a few drops of vegetable oil or conditioner to your hair – this stops the lice moving so rapidly.

You may prefer wet combing to insecticides, as it doesn’t involve using strong chemicals and it’s suitable to use if you have asthma or a skin condition, and for all ages. The Bug Buster comb is also reusable, so one comb can be used to treat all members of your family that are affected. However, wet combing isn’t as effective as using an insecticide treatment and it can be time consuming if you have many members of your family to treat.

There are also electronic nit combs available, but there isn’t any good evidence that they are effective so they aren’t currently recommended for treating head lice.

After treatment

Whatever treatment you use, you should check if it’s worked by detection combing two or three days after you have completed the treatment. Repeat this again after seven days. If you find any nits, it doesn’t necessarily mean that the treatment hasn’t worked – they may just be empty egg cases. If you find live lice, the treatment may not have been successful or you might have caught them again. You will need to repeat the treatment on your whole household. Lice can also become resistant to one or more insecticides, so you may need to switch to a different treatment.

If you’re pregnant or breastfeeding, you should treat head lice with wet combing or dimeticone 4% lotion. If these options don’t work, you might need to use a chemical insecticide. Always speak to your pharmacist or GP before using any insecticides.

Prevention of head lice

There is no good way of preventing head lice. The best way to prevent them spreading is to check your whole family’s heads for lice regularly. You can do this by detection combing on a weekly basis, or as often as you want. This may help you find any lice before they can breed and means you can treat them quickly to prevent them from spreading.

If you find a living, moving louse on one of your family’s heads, you should check all other members of your household carefully. This way, those who are infected can be treated at the same time.

You don’t need to wash clothing or bedding – head lice that fall off your head (onto hats or pillows) are likely to die soon after.


Reviewed by Dylan Merkett, Bupa Health Information Team, January 2014.

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For answers to frequently asked questions on this topic, see FAQs.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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