Adult head lice can live for approximately 24 hours away from a host, according to the Centers for Disease Control. Nymphs, or young head lice, can live for only several hours away from a host. Lice eggs are less dependent on a host, and they can live for up to one week without a host.
Certain conditions affect the length of time that lice eggs can survive without a host. For example, lice eggs cannot hatch in temperatures lower than that of the average body temperature, which is 98.6 degrees Fahrenheit. However, adult lice and nymphs are not affect by temperature changes.
Lice eggs take between eight to nine days to hatch. Once born, it takes about nine to 12 days for a nymph to mature and become an adult lice. Without treatment or removal from an infected area, the total lifespan of adult lice is 30 days. Adult female lice can lay up to six eggs per day.
Lice are a kind of parasitic insect that rely on consuming small amounts of blood absorbed through the scalp several times a day to survive. Lice are most commonly found at the base of the scalp. Lice spread through either direct contact with an infected individual, usually as head-to-head contact, or by coming into contact with items previously exposed to lice, such as hats, helmets and wigs.