Treating and Preventing Head Lice and Nits

Authored by , Reviewed by Dr Laurence Knott | Last edited | Meets Patient’s editorial guidelines

Treatment is needed only if you see one or more live lice. Empty eggshells (nits) do not always mean that you are infested with lice.

Nits can stick to hair even when lice are gone (for example, after treatment that kills the lice). You should only treat if you see live lice, not if you only see nits.

Currently, there are five main recommended options for clearing head lice, which work in three ways:

  • Mechanical method: wet combing using the Bug Buster® comb and method.
  • Insecticides which work in a physical way, by coating the lice and smothering them. Treatments which work this way include:
    • Dimeticone 4% lotion (trade name: Hedrin®).
    • Dimeticone 92% (trade name: NYDA®).
    • Isopropyl myristate and cyclomethicone solution (trade name: Full Marks Solution®).
  • Insecticides which work in a chemical way by poisoning the lice. In the UK the only one currently used is malathion 0.5% liquid (trade name: Derbac-M®).

The treatment chosen may depend on your personal preference and what you have tried before (if appropriate). Each treatment has a good chance of clearing head lice if applied or done correctly and if all affected people in the household are treated at the same time. Each treatment is briefly discussed below. However, for details of how to use each treatment, read the instructions that come with the packaging.

Dimeticone 4% lotion

Dimeticone is a silicone-based product. Dimeticone 4% (trade name Hedrin®) has a good safety record and is widely used in cosmetics and toiletries. You should apply the lotion to dry hair. This needs to be done twice - seven days apart. Each application is left on for at least eight hours (overnight) and then washed off with shampoo and water.

Dimeticone is thought to kill lice by a physical process rather than by any chemical effect. It is thought to work by blocking the tubes used by the lice to breathe and by blocking the way the lice pass out water, which kills them. However, it is not thought to kill unhatched eggs. This is why two applications are needed, seven days apart. The second application makes sure that any lice that hatch from eggs which survived the first application will be killed before they are old enough to lay further eggs.

Dimeticone is suitable for all ages, those with skin conditions and those with asthma. It is suitable for women who are pregnant or breast-feeding. It is available on prescription. You can also buy dimeticone over the counter (although not for children younger than 6 months of age). Over the counter, it comes in other formulations, such as a spray and a gel.

Dimeticone 92% spray

Dimeticone 92% spray (trade name NYDA®) is stronger than the 4% lotion and is thought to be more effective. It seems to be better at destroying eggs as well as killing adult lice. However, it should not be used if you are pregnant or breast-feeding. It also should not be used in children under the age of 2 years. It is available over the counter and on prescription.

It should be applied to dry hair and left for 30 minutes. After this, hair should be combed through with the comb provided to remove the lice. It is then left on for eight hours, before being washed off. Again, this should be repeated after seven days.

Isopropyl myristate and cyclomethicone solution

The trade name for this treatment is Full Marks®. It works in a similar way to dimeticone. You apply the solution to the scalp and leave in place for 10 minutes. The hair is then combed with a fine-toothed comb to remove lice. Then wash using shampoo to remove the solution. Treatment should then be repeated in seven days' time. The second application makes sure that any lice that hatch from eggs which survived the first application will be killed before they are old enough to lay further eggs.

This treatment is suitable for those with asthma. It is not suitable for children younger than 2 years of age or for people with skin conditions. It is not suitable for pregnant or breast-feeding women. It is available on prescription and also to buy over the counter.

Malathion 0.5% liquid

Malathion is a chemical insecticide that has been used for many years to treat head lice. The malathion kills the lice. There are various brands but the one available on prescription is Derbac-M®. You can also buy malathion over the counter (although not for children younger than 6 months of age).

It is suitable for all ages and those with skin conditions. It may be used in pregnancy but is only advised if you have tried wet combing and dimeticone 4% and they have not worked.

You should apply the lotion twice - seven days apart. Each application is left on for at least 12 hours (overnight) and then washed off with shampoo and water. The second application makes sure that any lice that hatch from eggs which survived the first application will be killed before they are old enough to lay further eggs.

Wet combing is a way of removing head lice without having to use a lotion to kill them. Briefly, the method is similar to wet combing (detection combing) described in the leaflet on head lice. But, you need to do this several times, four days apart. You will need to do this on every member of the household who has head lice.

It takes up to an hour to do a wet combing session properly. You need the correct toothed detection comb as described earlier. You can buy these over the counter at pharmacies. The Bug Buster® comb and method have been tested in research studies and the kit is available on prescription as well as over the counter. Only one kit is needed for a family, as it is washable and reusable.

  • Wash the hair in the normal way with ordinary shampoo.
  • Rinse out the shampoo and put on lots of ordinary conditioner.
  • Comb the hair with a normal comb to get rid of tangles.
  • When the hair is untangled, switch to the detection comb.
  • Slot the teeth of the detection comb into the hair at the roots so it is touching the scalp.
  • Draw the detection comb through to the tips of the hair.
  • Make sure that all parts of the hair are combed by working around the head.
  • Check the comb for lice after each stroke. A magnifying glass may help.
  • If you see any lice, clean the comb by wiping it on a tissue, or rinse it before the next stroke.
  • After you have combed the whole head, rinse out the conditioner.

You need to do the above routine at least four times, every four days. The number of sessions required depends on the last time you see lice:

  • The first combing session should remove all hatched head lice but does not remove eggs. Therefore, lice that hatch from eggs after the first session may still be present.
  • Subsequent sessions clear newly hatched lice. Keep doing the combing sessions every four days until you have had three sessions where no lice are detected.
  • Once you have had three sessions where you do not see any lice, it usually means that you are then free of lice.

Anybody of any age can have this treatment and it does not involve any chemicals. The downside to this treatment is that it is time-consuming.

Various other insecticides have been used in the past. For example, permethrin is no longer recommended for head lice because there are concerns that many lice are now resistant to it. Phenothrin and carbaryl are no longer available in the UK.

There are various other treatments that are said by some people to work. For example, tea tree oil, quassia, other essential oils, herbal remedies and electric combs. However, there is a lack of research studies to confirm that they work well in most cases. Therefore, until more research is done, these other methods cannot be recommended.

The wet combing method of treatment discusses above how to check for success. For other methods of treatment (lotions, sprays, etc), check that treatment was successful by detection combing 2-3 days after completing a course of treatment. Check again after a further seven days. Treatment has been successful if no lice are found at both sessions.

If your child has head lice, a common-sense approach is to tell the parents of their close friends to look out for lice in their children.

Children with head lice should carry on going to school. You need close head-to-head contact to pass lice on to others. Young children who play closely together may pass lice on.

Schools have a responsibility to give regular advice about head lice. School nurses no longer do regular nit combing.

There is no good way of preventing head lice. Lice repellent sprays do not work very well. If you do detection combing of children's hair every week or so, you will detect head lice soon after they have affected the hair. You can then start treatment quickly and reduce the risk of passing them on to others.

Only if they have head lice. All people who live in the same home and other close head-to-head contacts of the previous 4-6 weeks should be advised to look for lice. These people should only be treated if live head lice are found. They do not need "in case" treatment. All people with head lice in the same house should be treated at the same time. This stops lice being passed around again.

  • Use an anti-lice treatment only when you are sure that you have, or your child has, head lice. Do not use them to prevent head lice.
  • A common reason for head lice to come back in one person is because family and close friends are not checked for head lice. The treated person may then get head lice back again from untreated family or friends.
  • After treatment and when the lice have gone, it may take 2-3 weeks for the itch to go fully.
  • Nits may remain after lice have gone. They are empty eggshells and stick strongly to hair. They will eventually fall out. If you prefer, a fine-toothed 'nit comb' can remove them.

Head Lice and Nits

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Further reading and references

How to avoid back-to-school head lice
The best ways to get rid of head lice
Should schools or parents be fighting nits?

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