What to do about head lice
In the UK, you do not have to tell the school if your child has head lice. It makes sense to tell the parents of your child’s ‘best friends’, with whom they might have had head-to-head contact in the last 4–6 weeks. Friends do not necessarily need treatment – they need to be checked for lice, but not treated ‘just in case’. Do not use any treatments unless you are sure there are lice, that is, you have actually found at least one live louse.
Talk to your pharmacist, health visitor, school nurse or doctor if your child has eczema or asthma, and you are thinking of using head lice lotion, or if your child is under 4 years old.
How to get rid of head lice
- Read the label and follow the instructions exactly
- You will need to treat the head twice, with 7 days between treatments. This way, you will get rid of lice that have hatched from their eggs since the first treatment
- Do not use the lotion after you have been swimming, because chlorine can interfere with its action
- Put the lotion on dry hair, parting the hair into sections and combing the lotion through carefully
- Most head lice lotions are very flammable, and some horrible burns have occurred when people’s hair has caught fire. When you or your child have lotion on your hair, keep well away from fires, candles, gas cookers, pilot lights, matches and cigarette lighters
- Dry the hair naturally – hot-air hair dryers can deactivate the lotions, and a malfunctioning dryer could set the hair alight
- Wash it off 12 hours later.
- Repeat the treatment once more 7–10 days later to get rid of any newly hatched lice (because the first treatment will not kill lice eggs)
- Lindane was used as a head lice treatment in the UK for many years, but has now been withdrawn, partly because lice have become resistant to it worldwide, but also because of worries that it might promote cancers or cause nerve damage.
- Carbaryl (available only on doctor’s prescription in the UK) caused cancers when given to rats in large doses throughout their lives. Therefore it should not be used repeatedly.
- Malathion is an organophosphate insecticide. There have been concerns that organophosphates might damage nerves. However, the body breaks down and eliminates malathion very quickly. Official UK Government advice is that “malathion does not have the potential to cause a specific polyneuropathy because, unlike some other organophosphates, it cannot bind to the relevant target protein” (Communicable Disease Report, 1997).
- Permethrin and phenothrin are ‘pyrethroid’ chemicals that occur in chrysanthemum plants. (It has been known for centuries that chrysanthemum flowers can kill insects.) If these chemicals are absorbed by the body, they are eliminated very quickly and they do not appear to be dangerous. However, they may not be as effective as organophosphates (Archives of Disease in Childhood 2006;91:777–8).
Dimeticone is a lotion that kills lice by coating them with an oily substance; it is not a chemical insecticide like the older nit lotions. You can buy it from pharmacies. Apply it to dry hair making sure that all the hair is coated, leave the hair to dry naturally (without using a hairdryer), and wash it off after 8 hours. The treatment is repeated a week later to kill any lice that have hatched since the first treatment. It seems to cure about 70% of cases, which means it is more effective than the insecticide nit lotions (Drug and Therapeutics Bulletin 2009;47:50-2). The usual strength of dimeticone is 4%, but a much stronger version (92%) can be bought from pharmacies. Take care not to get this lotion into the eyes.
Isopropyl myristate is another non-insecticide lotion. It kills lice by blocking their breathing system and also dehydrates them. You apply it for only 10 minutes, then wash it out, and repeat the application a week later. The cure rate with isopropyl myristate seems to be about 80% (Drug and Therapeutics Bulletin 2009;47:50-2)
- Bug-busting is not as effective as lotions. Its cure rate is about 57% (British Medical Journal 2005;331:384–7) compared with 75% for lotion.
- It takes a long time to do bug busting properly. Each combing session will take about 30 minutes so do not try it unless you are willing to spend several hours a week on it.
- It is unsuitable for Afro-Caribbean hair – it would be difficult to do it properly and would be too uncomfortable. It is easiest on short, straight hair.
1.5-volt battery-powered combs are available from some pharmacies. The comb kills the head lice by making them lose their grip. It is unsuitable for children under 3 years of age or for anyone with an electrical device, such as a pacemaker. More research is needed to find out how effective this method is. It does not kill the eggs.
To use these oils, add six drops of a selection of the oils (three or four) to 30 mL (2 tablespoons) of sunflower oil. Massage it well into the scalp and leave for 6 hours. Then shampoo the hair and, when it is wet, go through it with a lice comb. Repeat every 3 days until you think the lice have gone.
It is difficult to know how effective herbal remedies really are, because there have not been any good scientific studies of them.
What to do if treatment is ineffective
- Maybe it has actually worked. Nits (the empty white eggshells) can remain after the lice are dead. Lotions do not get rid of the eggshells, and even special lice combs may not remove all of them, because the mother louse has fixed them very firmly to the hair. Itching can persist for weeks after the lice have gone, because it is caused by an allergy to louse spit. Remember that if itching is the only symptom, there may be another reason, and repeated use of head lice lotions could further irritate the scalp.
- The most obvious reason is that the treatment has not been carried out properly. For long hair, did you use enough lotion? Did you make sure the lotion saturated the scalp (where the lice live), not just the hair? Did you leave the lotion on for the correct time? Did you repeat the treatment 7–10 days later to get rid of newly-hatched lice? If you were bug-busting, did you do it thoroughly, or were you fed up and half-hearted?
- It is possible that your child has simply caught lice again.
- Some head lice are resistant to one or other of the head lice lotions. So talk to your pharmacist, school nurse, health visitor or family doctor, and try one that contains a different chemical. Because the new dimeticone and isopropyl myristate treatments work by smothering the lice, resistance is unlikely to develop.
Bug-busting is not 100% effective. If some lice remain, after a few weeks they will multiply. But using this method will certainly keep the numbers down, even if it does not eliminate them entirely.
Ways of preventing re-infection
- Tell the parents of ‘best friends’ that your child has head lice, so they can be checked.
- Check everyone in your family, but treat them only if you find live lice.
- Think about your choice of treatment. Malathion is absorbed into the keratin of the hair and skin surface, and gives protection even after you have washed it off. This effect dwindles away over about 6 weeks. Permethrin and phenothrin (but not carbaryl) also have a protective effect lasting several weeks.
- Get into the habit of brushing and combing your hair thoroughly twice a day. This might kill some lice.
- Wash the hair three times a week, apply conditioner and, while it is wet, comb through carefully with a plastic lice comb. This will kill some lice and help prevent re-infection.
Written by: Dr Margaret Stearn
Edited by: Dr Margaret Stearn
Last updated: Monday, March 7th 2011
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In the UK, each month 20% of hairdressing salons see head lice in a client's hair
An estimated 5% of the UK population has head lice
Each year in the UK, the NHS and the general public together spend £29 million on head lice treatments
'Lousy', 'nitwit', 'nit-picking', 'nitty-gritty', 'go through something with a fine-tooth comb' - all these phrases come from lice
The average person with head lice has about 20 lice. During their 30-day life, 20 lice will lay 2652 eggs (Lancet 2003;361:99-100)
After mating, a female head louse keeps spare sperm in a special container in her body (spermatotheca), so that she does not have to bother with mating again, but can use the sperm she has kept (Lancet 2003;361:99-100)
Head lice are fairly speedy. They can move at 23 cm per minute (Lancet 2003;361:99-100)
Head lice have probably been annoying humans for at least 72 000 years (New Scientist 2003;23 Aug)