Head lice are small parasitic insects found on the heads of people.
Head lice derive nutrients by biting and eating blood several times each day, and cannot survive for more than a day or so at room temperature without ready access to a blood meal. They are head lice eggs that are attached to the hair shaft. They are difficult to see and are white or yellow. They can be mistaken for dandruff. Nits take about 1 week to hatch.