Head lice

Produced by Alice Rossiter, Bupa Health Information Team, February 2012.

This factsheet is relevant for adults who have head lice and parents of children with them. However, for simplicity we will refer to 'you' throughout.

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 tan to greyish-white in colour and have hook-like claws that hold onto your hair. Adult head lice are around 1mm to 3mm in length – about the size of a sesame seed.

Female head lice lay eggs, known as nits, which attach to your hair shaft. The nits take about a week to hatch. Young lice are called nymphs – they take about seven days to mature to adults and feed on blood from your scalp to survive. Adult lice can live for up to 30 days. Head lice infestation varies from a few lice to thousands, but a typical infestation is around 30 lice per head.

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 if you find a living, moving louse on your scalp.

Symptoms of head lice

You usually don’t realise you have head lice until your scalp becomes itchy – this can take from one week to three months after initial infestation. You might get a tickling or itching feeling, or the feeling of something moving in your hair. You might develop a rash behind your ears and at the back of your neck – this is caused by a reaction to the louse faeces. If you scratch a lot, you may also develop skin sores, which can become infected. You might also see nits stuck to your hairs shafts as they grow out.

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 for infestation is between seven and eight.

Other risk factors for head lice infestation include:

• being female
• living in a household with four or more children
• having long hair
• being younger than 12

Studies have shown that black African American people are less likely to get head lice.

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. It’s extremely rare 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 only have head lice if you can find a living louse on your scalp. They can be hard to spot, but you can comb your wet or dry hair using a special, fine-toothed comb to remove the lice and confirm that you have them. This is called detection combing and it’s normally easier to do when your hair is wet. Applying conditioner to your hair can be helpful because the lice can’t move as quickly and so are easier to see on the comb. After each stroke, check the comb for lice. It takes around 15 minutes to wet comb your head.

If you do detection combing on dry hair, you can place your thumb on a louse if you find one before pulling the comb through and out of your hair – this will stop the louse being flicked off the comb. If you find any lice when combing, you can attach them to a piece of sticky tape to take to your GP or a health professional (such as a school nurse or a pharmacist) if you’re unsure what you’re looking for. 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 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 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 most successful when you apply the treatment correctly and all 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 their surfaces. 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.

Isopropyl myristate and cyclomethicone (Full Marks Solution)
This is a physical insecticide. You leave the solution on your hair and scalp for 10 minutes before combing your hair through with a fine-toothed comb to remove lice. The treatment is then washed using shampoo. Full Marks Solution is suitable to use if you have asthma, but not if you have a skin condition or for children under two.

Coconut, anise and ylang ylang spray (Lyclear SprayAway)
This is a physical insecticide that is left on your hair and scalp for 15 minutes, and then washed out using shampoo. You then comb your hair through with a fine-toothed comb to remove the lice. Lyclear SprayAway isn’t suitable if you have asthma or a skin condition, or for children under 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. It’s suitable to use if you have a skin condition, but 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 infested. 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 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, and once 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 GP or your pharmacist 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 will help you find any lice before they have a chance to breed and lay nits. You can then treat them quickly to prevent them from spreading to other people.

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, because head lice that fall off your head (for example, onto hats or pillows) are likely to die soon after.

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

For sources and links to further information, see Resources.