Head lice infestation is a condition caused by a parasitic insect. Live lice can be found anywhere on the scalp; the eggs are most commonly found behind the ears and at the back of the neck. The severity of infestation varies from a few lice to thousands of lice, but a typical infestation might have about 30 lice per head. Head lice infestation is most common in children 4–11 years of age.

Confirming active infestation of head lice includes systematic combing of wet or dry hair with a head lice detection comb. A live louse must be found in order to confirm active head lice infestation. An itching scalp is not sufficient to diagnose active infestation.

The presence of louse eggs alone, whether hatched (nits) or unhatched, does not indicate active infestation as it is hard to distinguish between dead and live eggs with the naked eye, and eggs may maintain a viable appearance for weeks after death.

All members of the household and close contacts should also be checked for head lice as untreated family members and close contacts may cause re-infestation in the people, who have been treated.

Treatment of head lice
First line treatment is Dimeticone 4% lotion (Hedrin) which is a physical insecticide. This can be purchased over the counter or be given as a prescription. It is rubbed into dry hair and scalp, allowed to dry naturally, shampoo is applied and rinsed off after at least 8 hours (or overnight). A repeat application is needed after 7 days. This prescription can be given by a Health Visitor or a GP.

British Association of Dermatologists
The NHS website – Head lice and nits
Torbay health and care videos – finding and treating headlice