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Head lice are wingless insects that live on the scalp and neck. They are grey or brown, have six legs and are about 2 mm long when fully grown. There can be up to 12 adult head lice on an infested scalp at any one time. They may be embarrassing and occasionally uncomfortable but head lice are not generally a cause of illness.
Head lice live for about three weeks and the female can lay up to six eggs a day. She attaches them to the hair near the scalp and they hatch 7-10 days later. The unhatched eggs, which are called nits, are a yellow-white colour and are often mistaken for flakes of dry skin or dandruff. However, unlike dandruff, the nits stick to the hair and are difficult to remove.
Headlice should only be treated with insecticides when a living, moving louse has been found.
About 80% of head lice infections are amongst children aged 4-16 years. They are usually caught via head-to-head contact, or more rarely by sharing hairbrushes, combs or hats. However, head lice cannot survive for long away from the scalp and those found in clothing are usually dying.
Head lice can be found in all types and lengths of hair. It is a common mistake to associate a head lice infection with dirty hair. They are equally happy living in clean hair.
Head lice infestation can cause an itchy head or neck or a rash, which is often worse behind the ears or on the back of the neck. However, a person may have been infested for several months before the itchiness is noticed, and some people may not report itching at all. Its important to check anyone who has been in contact with a confirmed case of head lice so that all cases can be treated and reinfestation prevented.
Other signs of head lice infection are nits stuck to the hair as they grow out, and the louse droppings, which look like a fine black powder and may be seen on pillows or sheets. If nits or droppings are spotted then further investigation is required.
Head lice are easier to detect on wet hair. The hair should be combed in sections using either a fine-toothed comb or a special nit comb – available from pharmacists. The hair may be easier to comb if conditioner is used (this should be rinsed off afterwards). It is important to comb the entire length of the hair from root to tip. After each stroke, the comb should be checked for lice. The hair may also be combed over a piece of paper or a bowl of water, which can then be checked for lice.
If a living head louse is found, its a good idea to tape it to a piece of paper and get the infection confirmed by a health professional (a school nurse or pharmacist, for example), who can advise on suitable treatments.
Once a head lice infection is confirmed there are a number of treatments available:
- Thorough and frequent combing (bug-busting)
- "Alternative" treatments
The insecticides and alternative head lice treatments can be strong chemicals with the potential to cause side-effects. They should only be used on a confirmed head louse infection. When a confirmed infection is found in a household, all family members should be checked and anyone who has lice should be treated. Because of potential side-effects it is not a good idea to treat the whole family as a preventive measure. Insecticides and alternative treatments should only be used according to the instructions.
Some types are available over the counter, such as Malathion Vickmans and Quellada.
These insecticides are available in shampoos, lotions and liquids or cream rinses. Shampoos are not considered effective. The most effective insecticides are alcohol-based lotions, but these are not suitable for everyone. Liquids or cream rinses are water-based and are recommended for young children and for people who get asthma or eczema. Pregnant or breast-feeding women should check with their doctor or health visitor before using insecticides.
Resistance to insecticides has been reported and if one treatment fails, then another should be tried. A health professional or pharmacist can advise which is the best insecticide to use in a given area.
The treatment involves rubbing the insecticide lotion onto the scalp and hair and leaving it for a minimum of 12 hours before washing out. This will kill the living lice, but may not kill the eggs. The treatment should be repeated a week later to destroy any lice that have since hatched.
Combing, or "bug busting"
This is a method of removing lice with the regular use of a fine-toothed comb. Its effectiveness has not been scientifically tested, but success has been reported where families are highly motivated and follow the instructions carefully. This treatment method requires four sessions over two weeks. The advantages of this method are that it avoids the use of strong chemicals, and lice cannot become resistant to it. It can also be used for routinely checking the hair for infection.
These such as those containing essential oils (including tea-tree), herbal extracts or homeopathic tinctures are also available. There is little robust scientific evidence for these treatments, but some people find them helpful. It is worth bearing in mind that even "natural" chemicals can cause side-effects, such as irritating the scalp.
Whichever treatment is used, a follow up check using a nit comb should be carried out a few days afterwards. The presence of eggs does not mean that the treatment has failed. And even if a live adult louse is found, this may be due to reinfestation rather than failure of the treatment.
However, treatment does sometimes fail – usually because of incorrect or inadequate use. If this happens, the infestation will have to be retreated, possibly with a different method.
1. 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.
2. 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.
3. 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.
- Community Hygiene Concern
- National Center for Infectious Diseases
- Health Protection Agency
- Community Hygiene Concern
01908 561 928
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