Overview
Head lice (pediculosis capitis) is an infestation of the human head louse, which results in intense itching on the scalp. The itching is the result of a reaction to the bite on the scalp. Head lice is passed through direct (head-to-head) contact and also by touching contaminated objects and then touching one's head. Head lice is highly contagious, and outbreaks are often seen in nurseries and day-care centers.
The human head louse is a tiny (about 2–4 mm long) insect that feeds on human blood. The female lays eggs (nits) on the hair shaft close to the scalp; they are glued to the hair but do not touch the body. The adult louse is often not visible, but the nits can be seen with the naked eye. When the nits hatch about 8–10 days later, they also begin to feed. Lice is highly contagious because the nit can stay alive for a long period of time off of the body (such as on hairbrushes, furniture, or linens), which increases the time that it can be transferred to another child.
