Head lice, though common, still make most parents, teachers, and health-care workers uneasy. The good news is that head lice usually do not cause any serious disease and can be treated easily. The common head louse is an insect which attaches itself to the scalp and feeds on human blood. A louse is tiny and mobile, and can be hard to spot, especially in individuals with thick hair. Lice lay eggs on the shafts of hair, and often it is these small white “nits” that are the first indication of an infestation.