A parasitic infestation of the head, the hairy parts of the body and the clothing by adult lice, larvae and nits (eggs), which often results in severe itching and excoriation of the scalp and body. Secondary infection can occur. Infesting agents include Pediculus capitis, the head louse, P. humanus, the body louse, and Pthirus pubis, the crab louse, which usually infest the pubic region, but may also infest the hair of the face, axillae and the bodysurfaces.... pediculosis