Nit eggs hatch six to nine days after they are laid. After a nit egg hatches, it releases a nymph, which grows to adulthood in seven days. Adult female lice can lay up to eight nit eggs daily. Adult lice can live up to 30 days on a human scalp.
Adult lice feed on blood multiple times each day. Without a host, an adult louse dies within one to two days. Nits must be kept at the temperature that is found close to the scalp to survive. Nits that fall off of the head normally cannot survive and die within a week.