Now that children are back at school, parents can steel themselves for that letter from the school principal advising them of an outbreak of head lice in the classroom.
Contrary to popular perception, the presence of head lice in a child's hair does not indicate poor personal hygiene. Lice prefer clean hair.
I recently received an email from a colleague, containing the following plaintive message: "Over the past six weeks I have tried Permethrin, Malathion, (two drug treatments), fine combing, vinegar, lemon juice, and electronic fine combing and still the problem persists. I dread to think what will happen when school starts. Have you any advice?"
This doctor's experience is not unusual. Head lice are difficult to treat. They cannot be washed away because of the glue-like substance they use to latch onto the individual hair. There is also evidence to suggest that the lice become resistant to some of the standard drug treatments.
Head lice - or pediculosis capitis - are small, wingless parasites. Flat in shape, they range in colour from brown to white. They have six legs, with a small claw at the end of each leg. They can live for up to 30 days.
Head lice cannot fly or jump and can only be passed from one individual to the next by direct head-to-head contact. The female lays six to eight eggs each night and glues them to the base of a hair. Seven days later, the baby louse hatches, leaving behind a shell which is known as a nit.
After 19 days the young louse is mature enough to reproduce and so the cycle continues. Lice feed off human blood in the scalp which causes intense itching, especially behind the ears and at the nape of the neck.
When looking for lice in a child's hair, use natural light, as they tend to shy away from bright, artificial light. Examine behind the ears for scratch marks. Look for small, yellow, brown or white specks attached to the hair near the scalp.
There are many treatment options available. Drug treatment involves using a special shampoo or lotion. Malathion, according to a recent review in the Lancet medical journal is twice as effective as other treatments. It is available under the following trade names as 0.5% solution: Derbac, Prioderm and Quellada.
Permethrin is another effective treatment marketed as Lyclear Cream Rinse. It is available in a form of a conditioner and is suitable for children over six months. Apply enough to saturate the hair and scalp and leave for 10 minutes. The conditioner must be rinsed thoroughly and the hair fine-combed while wet.
Malathion is available as a lotion and should be rubbed into hair and left for 12 hours before shampooing and then combing while wet. The entire process should be repeated after a week.
When doctors are faced with a major outbreak of head lice in a particular area, they will usually try to rotate the use of different treatments to avoid the drug resistance which can be a problem in treating this condition.
Some parents do not like the thought of using chemical treatments containing organophosphate. About two per cent of the chemical is absorbed by the scalp, most of which is converted to a non-toxic product. An alternative is to wash the child's hair with conditioner once or twice per day. Conditioner makes it difficult for the lice to maintain a foothold, so that rigorous combing will eventually get rid of the infestation. However, this is a labour-intensive approach requiring perseverance and patience. A combined chemical and combing effort is best.
If the child's hair is particularly long, cutting it will also help. There are electronic fine combs on the market which give a characteristic sound when they locate a nit. However, a simple systematic combing of the entire scalp is sufficient.
Treating the entire family is a must. Mum, dad and other adults who live with the child should undergo the full treatment regime. Itch may persist for some days after the head lice have cleared; do not misinterpret this as a sign of treatment failure.
However, head lice can be hard to eradicate, so it really is a case of: if at first you don't succeed, try, try again.
Contact Dr Houston at mhouston@irish-times.ie or leave messages on tel 01-6707711, ext 8511.