Head lice are tiny wingless insects that live in hair. They are grey-brown in colour and about 2.5mm long, which is the size of a sesame seed, when fully grown. Head lice cling to hair and are usually found on or near to the scalp.
Lice themselves are not to be confused with nits - the empty egg cases from which they hatch. A nit (louse egg) is of a similar size to a small flake of dandruff.
Head lice are a common problem, particularly in school children aged. Between 8 and 10% of children in the UK have head lice at any one time (1).
Head lice pass from one person to another during direct head-to-head contact. This is because lice cannot fly, jump or swim and most often are transferred to another head by climbing from the hair of an infected person to the hair of someone else. Head lice only affect humans and cannot be passed on to animals or caught from them.
Contrary to popular belief, they have nothing to do with dirty hair and can be contracted by even the cleanest people.
A female head louse lays eggs by cementing them to hairs, where they are kept warm by the scalp. After 7 to 10 days the nymph louse hatches out of the egg, leaving a shiny white empty eggshell (nit), which may be found anywhere along a strand of hair. Head lice feed by biting the scalp and feeding on blood. They take 9 to 12 days to become fully grown. Once mature, they can move from head to head if direct contact is made. Head lice typically live for about 25 to 35 days. A female head louse can lay eggs as early as 7 days after she has hatched and will produce 4 to 6 eggs per day. To break the cycle and stop lice spreading, head lice need to be removed within 7 days of hatching.
'Live' head louse eggs are each glued to an individual hair strand as soon as they are laid. Nits are the empty egg cases, which remain glued in place on the hair as it grows out after the nymph lice have hatched. Nits are often the first visible sign of a head lice infestation.
Often there is no sign of infestation until nits, which are hatched empty egg cases, start to become visible within the hair. In most cases, itching is the main symptom of head lice, which is not caused by the lice biting the scalp but by an allergy to the lice saliva. However, not everyone experiences itching and it can take up to three months to develop this allergic reaction to the lice saliva. In some cases, a rash may appear on the back of the neck. This is caused by a reaction to lice droppings.
Further symptoms include a red rashes and little red bumps as well as difficulty sleeping - this due to lice crawling through the hair.
It is not always easy to see head lice, even when the head is closely inspected. Unhatched eggs or nits (empty shells) alone are not enough to diagnose an active head lice infestation. This is because it can be difficult to distinguish between eggs and nits that are dead or alive. Nits can remain glued to the hair after successful treatment. To confirm an active head lice infestation, a louse must be found and the most reliable method to use is “detection combing”.
Detection combing can be carried out on dry or wet hair. However, wet combing is more accurate because lice remain motionless when wet and if hair is conditioned lice become immobilised. The following steps should be taken:
If head lice are found, parents are advised to check every family member.
It is difficult to prevent a head lice infestation because head lice are spread by head-to-head contact. Regular detection combing on a weekly basis is the best way to find new head lice quickly. Alternatively, if there’s a risk of head lice from an outbreak at school, or in advance of a sleepover, a trip away, or if someone in the family is affected, a protective shampoo may be used. Vamousse Protective Shampoo helps protect against a head lice infestation growing larger by killing them before they lay eggs.
Treatment should be carried out only after live head lice have been found. Head lice can be difficult to treat due to a high re-infestation rate and their ability to develop resistance to traditional insecticides/pesticides contained in some medications. Treatment options include wet combing the hair using a head lice comb (tooth spacing of 0.2-0.3mm) or by using mousse, lotion or spray (see below). However, neither will protect against re-infestation if head-to-head contact is made with someone who has head lice during the treatment period.
The wet combing method involves removing the head lice by systematically combing the hair using a special fine-toothed comb. The comb's teeth should be spaced 0.2-0.3mm apart. For wet combing to be effective, it needs to be regular and thorough. Follow the “detection combing” method and repeat the procedure on days 5, 9 and 13, so that you clear young lice as they hatch, before they have time to reach maturity.
Follow instructions that come with the mousse, lotion or spray when applying it. Depending on the product you are using, the length of time it will need to be left on the head may vary, from 10 minutes to 8 hours. Also depending on the product, you may have to repeat the treatment after seven days.
If the lice appear unaffected by the product (some lice may develop resistance to particular insecticides/pesticides), or if the problem persists, seek advice from your school nurse, health visitor, pharmacist or GP.