When an infestation occurs there may be up to 12 adult lice on the scalp at any one time. A female louse can lay eggs at the rate of about six per night up to a total of 100. The yellow-white eggs, called nits, are stuck to the hair close to the scalp. Nits can often be mistaken for dandruff, flakes of dry skin or other small items caught in the hair.
Head lice can also survive for short times on bedding and furniture.
Children are particularly prone to infestation with head lice as they often have close contact with each other at school or when playing. There is no link between the presence of head lice and a lack of hygiene or susceptibility to infection. Often the first sign of infestation is an itchy head or neck. The saliva of head lice is irritating on the skin, and itching is often worse behind the ears or at the back of the neck. However, head lice do not always cause itching.