Head lice affecting the scalp (Pediculosis capitis) is a very common problem, especially in school children. There are various treatments, but whatever approach is used they can be a persistent or recurring nuisance.

The main symptom, if noticed by the individual, is an itchy scalp. This is sometimes especially so behind the ears.

The cause is a tiny insect which lives on the scalp, and feeds by sucking blood through the skin. The head louse grips on to the hair with its six tiny claws.

The female lays its eggs (nits) in sacs which are glued to a hair. These take seven to ten days to hatch. The lice then take seven to fourteen days to become mature and ready to reproduce. The total numbers of lice thus rise very quickly.

Head lice do not jump, fly, or swim. They spread by direct contact, "walking" from one hair or head to another. They happen in the best circles, and do not mean that you or your child are unclean or dirty, in fact some people say that head lice prefer clean heads.

About half of the children affected will notice itching of their scalps which draws attention to the problem. The lice themselves are small, about the length of a match head, and may be difficult to see, as their colour is often close to the hair colour.

Newly laid eggs are usually close to the scalp (about 1.5cm or about 0.5in) and as the hair grows this, and subsequently the empty sac, once it is hatched, will move further from the scalp.

When the egg is still in the sac it is small and rather dull in colour, and difficult to see. Once the egg has hatched (7-10 days) the sac is white and easier to see.

Head louse (Pediculus capitis) only affects humans, and cannot be passed on to, or caught from animals.

The best way to check on the presence of lice, if you are not sure, is to use the following lice detection regime:

1. Wash the hair as normal.
2. Apply conditioner liberally, including the full length of long hair.
3. Lay out white tissues over which you will comb the hair.
4. Comb the hair through with a normal comb first, to get rid of any knots.
5. With a fine tooth comb ("nit comb"), starting from the roots of the hairs, comb out along the complete length of the hair. After each stroke check the comb for lice and wipe it clean. Work systematically around the whole head of hair.
6. Rinse the hair as normal.

Firstly, don't panic! Most times you can make the diagnosis and start the treatment yourself, but if in doubt, or if the lice seem resistant to treatment, consult the pharmacist, nurse (attached to the school or your doctor's surgery), health visitor or doctor.

There are various proprietary, active treatments available, and so-called "bug-busting".

There is no need to wash or specially treat clothing or bedding that has been in contact with head lice. They need warmth to survive and within hours of leaving their host they dry out and become unable to reproduce.

Treatments all have the potential for unwanted side effects, and you should discuss the pros and cons with the pharmacist, nurse or doctor. In addition to unwanted side effects there is an increasing problem with lice that are resistant to the effects of the treatments.

Bug-busting

"Bug-busting" consists of the approach listed above for detection of lice, repeated at regular intervals.

1. Wash the hair as normal.
2. Apply conditioner liberally, including the full length of long hair.
3. Lay out white tissues over which you will comb the hair.
4. Comb the hair through with a normal comb first, to get rid of any knots.
5. With a fine tooth comb ("nit comb"), starting from the roots of the hairs, comb out along the complete length of the hair. After each stroke check the comb for lice and wipe it clean. Work systematically around the whole head of hair. Continue for at least 30 minutes.
6. Rinse the hair as normal.
7. Repeat every two to four days for at least two weeks.

The conditioner causes the louse to lose its grip on the slippery hair, and also probably blocks the breathing apparatus (spiracle). This treatment has the benefit of not exposing the person to unnecessary chemicals, and reduces the likelihood of the lice becoming resistant to medications.

Physical insecticides

There is some evidence that physical insecticides might be more effective than the more traditionally used insecticides. They work physically, rather than chemically, by smothering the lice. Adverse side effects are mild and uncommon.

• Dimeticone (Hedrin, NYDA)
• Isopropyl myristate and cyclomethicone (Full Marks Solution)
• Coconut, anise, and ylang-ylang spray (Lyclear SprayAway)

Chemical insecticides

Chemical insecticides, such as malathion (Derbac-M), have greater potential for side effects and the head lice are increasingly resistant.

Not recommended:

• Benzyl benzoate, less effective.
• Permethrin, resistance is developing and the 10 minute contact time is thought to be too short.
• Insecticide shampoos are not recommended as they are too dilute when used to be effective against head lice.

It is probably worth checking your child for lice weekly, and undertaking treatment if any are found.