Lice will leave the head when there is physical contact with another head, when they are removed by combing or brushing, and when they are carried off as a hat is removed. Head lice are a community problem. The adult female head louse lays her eggs at the base of the hair. The eggs hatch in about eight or nine days. The young lice and adults live their entire lives on the head, sucking blood for food.
Head lice are completely dependent on human heads for warmth and food.
They need about five blood meals each day and lay six to eight eggs a day. Head lice live 30 to 40 days at the most. Head lice will die in one or two days when removed from the head, and eggs will die soon after being removed from the warm scalp. Head lice are more common in children 3 to 12 years old and become progressively less common as children grow older. There are no economic barriers to the head louse.