Three kinds of lice with similar characteristics infest humans. Body lice are largest. They are wingless insects with three pairs of legs. Legs terminate in sharp claws adapted for feeding and grasping.

Infestations of the eyelash are seen almost exclusively in children. It may induce blepharitis with lid pruritus, scaling, crusting, and purulent discharge.

Head lice are most often found in the occipital areas. Nits are deposited on the shaft 1 cm above the scalp surface. Excoriated lesions may become crusted and infected.

Nits are lice eggs that appear as white, firmly attached bumps.