The nymphs molt three times before reaching maturity. In order to survive, lice require temperature and humidity conditions similar to those found associated with human bodies. They dry out rapidly if they are away from people for more than 24 to 36 hours. Head Lice Head lice live on the skin among the hairs on people's heads. Nits hatch in 5 to 10 days, and the light-colored nymphs begin feeding immediately.
Head lice have little real medical impact.
Their feeding activity irritates the scalp, causing intense itching. They are not known to transmit any disease organisms, but a secondary infection may result if the skin is broken by repeated scratching. Children, particularly those of elementary school age, are most likely to get head lice because of their close contact and social interactions with each other. Nursing home residents and other people sharing close quarters and bathing and communal facilities are also likely to get lice. Sharing combs and brushes creates opportunities for the spread of lice.