Head lice

 

What are they?

A head louse is a small wingless insect, Pediculus humanus capitis, which lives on the human head. It clings to the hair shaft with its claws and sucks small amounts of blood from the scalp to survive.

How do head lice occur?

Female lice lay eggs at the base of the hair shaft close to the scalp. These take about 10 days to hatch and then 10 more days to develop into a fully-grown adult louse. It is nearly as big as a match-head and grey-brown in colour. Each louse lives about two or three weeks in all.

Lice are caught by head-to-head contact, which is why they are most common in children aged between four and nine, and why outbreaks tend to occur in schools and in families. About one child in every 10 has head lice but adults can get them too.

Lice crawl. They cannot jump, fly or swim and so are not spread by long hair or in swimming pools.

 

What are the symptoms?

Not everyone with head lice has symptoms:

Itching

About one third of people with head lice have itching of the scalp, which can be intense and is due to an allergic reaction to the louse bite. Allergy can take three months to occur so itching is not a reliable early symptom.

Visible lice

It may be possible to see lice moving on the hair, especially the crown. However, if there are only a few lice - and 10 per head is about average, they can easily be missed.

Presence of louse eggs

There may be louse eggs visible close to the scalp. These are dull, often the same colour as the hair, and about the size of a pinhead, so they are harder to see than live lice.

Other signs

Sometimes there can be a little gritty black or brown powder left on pillows, sheets and clothing; this is the remains of the blood digested by lice.
Nits are the empty egg cases left after a louse has hatched. They are white and can look a bit like dandruff, but unlike dandruff scales, nits are shiny and are not easily removed from the hair. The presence of nits does not mean active head lice, although it does mean that there has been an infestation.

What are the complications?

Since head lice can cause itching, one possible complication is scalp infection carried from fingernails. This can lead to sores, blisters or even impetigo, which may need treatment.

The most common complication however is simply the risk of passing lice onto another person by head-to-head contact.

Unfortunately, head lice can cause a great deal of anxiety for parents, who may consider the infestation a social stigma. But head lice are just a very common problem. There is no connection with poor hygiene, and anyone can catch them, regardless of social background and lifestyle.

 

What tests are done?

There are no laboratory tests for detecting head lice, but a routine combing check can be done at home for children. Once a week is often enough to check, although if there is a lice alert at school or if someone else in the family has head lice, then a daily check is a good idea.

The check is best done by combing damp hair carefully with a special fine-toothed louse detection comb (with teeth less than 0.3 mm apart), over a white surface like a paper towel, white bath-tub or hand-basin, to see what bits the comb brings out. If parents are uncertain about the identity of what has been produced, the debris can be stuck to clear adhesive tape and taken to the health visitor or GP for an opinion the next day.

What is the treatment?

There are several approaches to consider. It is essential for effective treatment that all members of the family are treated, and not just the children, as re-infection from an untreated parent is possible. So, whatever the treatment of choice, remember to include the whole family.

There are several approaches to treatment. These include:

  • insecticides;
  • physical methods; and
  • alternative methods.

Head lice may become resistant to any form of treatment and it is recommended that should one form of treatment fail, then an alternative treatment should be pursued. Whatever the choice of treatment, it is important that the application is applied thoroughly to the hair. Insecticides applied to the head kill both lice and eggs and are the quickest way of treating head lice.

There are three main types:

  • Carbaryl;
  • Malathion; and
  • Pyrethroids (such as Permethrin and Phenothrin).

These come in various formulations. Lotions tend to work better than shampoos, and alcoholic formulations can temporarily worsen asthma. Some treatments are inactivated by heat, so a hair dryer cannot be used. The instructions supplied with each product makes it clear what to do, and which age groups can be treated.

Research suggests that Permethrin is very effective. Malathion is an organo-phosphorus chemical, which is absorbed to some extent through the skin and twice as effective as bug busting (see below). For this reason, it should be used once weekly as a maximum, and for no more than three consecutive weeks. Carbaryl is prescription only and tends to be reserved for infections that do not respond to other treatments.

Resistance to insecticides is a growing problem. The pattern of resistance varies across the country, and the current best advice is to check with your general practitioner or pharmacist which insecticide is recommended in your area.

Do not use medicated lotions or rinses unless head lice have been diagnosed. Overuse of these products when they are not really needed does not help prevent you from getting head lice.

An essential part of treatment is checking the rest of the family, and telling the child's school, play group or child-minder. There is no need to seek urgent treatment or an immediate consultation with the doctor unless the complication of scalp infection is a problem. Children need not stay away from school.

 

What physical methods of treatment are there?

Unfortunately, chemical treatments can fail, either because not all the lice are killed, or because they have become resistant to the particular product used.

A treatment that is becoming more favourable and is being recommended by the Department of Health is 'bug busting'. It can be very effective but is not yet supported by any published scientific evidence, as it is a natural approach.

This approach aims to remove the live lice in a systematic way by combing through the hair and physically removing any lice. The treatment takes the form of four spaced sessions over a two week period to clear the lice.

The logic behind the bug busting or combing method is to break the legs of the lice by prolonged wet combing. This is done with a plastic louse detection comb on hair that is saturated with ordinary hair conditioner, until the lice come out. It should be done for half an hour each time, and repeated every fourth day for two weeks at least (more if any lice are found after the first combing session).

As yet, there are no large controlled studies to support this method. However, parents are often attracted to it because it does not involve drugs. It does demand a lot of co-operation from the child as well as commitment from the parent, especially if several members of the family need treatment.

What alternative treatments are there?

Many complementary therapies, including tea-tree oil, quassia, herbal remedies, essential oils and even petrol, have been advocated for head lice. There is no good evidence that any of these works. Petrol is obviously extremely dangerous.

Electric combs are available. These are said to break the grasp of the louse on the hair, making it removable, and may kill the louse as well. There is no scientific evidence that these work any better than wet combing.

 

What lifestyle measures are advisable?

Lice need humidity and warmth (a temperature of at least 31 degrees Celsius) so they cannot survive on, or be spread by any objects. There is therefore no point in throwing away or burning clothes, towels or combs, hair slides and other hair accessories after head lice have been found.

Nor is there any need to cut long hair. Wearing hair short or tying long hair back is often suggested, as it may reduce the chance of contact with an infested head, but it does not necessarily prevent head lice. Girls tend to get head lice more than boys, but this is probably because they have more prolonged head-to-head contact.

Essential oils have been advocated as a way to repel lice and prevent an infestation. They can be an irritant to some people, and there is no conclusive evidence that they are effective. The best way to ward off head lice is for parents to be vigilant and check the hair of primary school age children regularly. There is no need for this to be done by a school nurse or health visitor.

 

Where can I get further information?

For more information on bug busting, contact:

Community Hygiene Concern
Manor Gardens Centre
6-9 Manor Gardens
London
N7 6LA
Helpline: 020 7686 4321
Website:www.chc.org/bugbusting

'Bug buster' kit includes an illustrated guide and combs.