The presence of lice in the hair on the head.

Head lice infestation is caused by insects called lice that feed on blood from the human scalp. Lice spread by direct contact, most often among children. Lice also may spread through sharing items that touch the head or storing these items with other clothes.

Head lice infestation symptoms often include itching on the scalp, head and ears. This may cause sores. People also may see lice on the scalp or lice eggs on the hair.

Head lice infestation is treated by repeat applications of medicine that kills the lice. Some medicines are available without a prescription. Other medicines are available with a prescription from a healthcare professional.