Pediculosis capitis or head louse is caused by infestation of scalp with the highly host-specific insect, Pediculus humanus capitis. The highest incidence occurs in school-aged children, primarily girls, aged 3-12 years. The most important mode of transmission remains direct head-to-head contact for a prolonged period. The head louse is 1-2 mm in length, dorsoventrally flattened, and elongated with narrow sucking mouthparts hidden inside the structure of the head. It has three pairs of clawed legs that are adapted to grasp hairs.