Head lice are tiny insects that live only on people's scalp and hair.
They look like grains of sand. Nits may be found throughout the hair but are most often located at the back of the scalp, behind the ears, and at the top of the head. The eggs hatch in about 10 days, with new lice reaching adulthood in about 2 weeks. The female louse is about the size of a sesame seed, can live for 20 to 30 days, and can lay about six eggs a day. The lice live by biting and sucking blood from the scalp.