Pediculosis and scabies. What to look for in patients who are crawling with clues.

Lice and mites are highly contagious obligate parasites of humans and are spread by close, direct contact. Head, body, and pubic lice produce severely pruritic eruptions in their respective locations. Diagnosis is readily made by finding lice or nits on hair shafts, except in the case of body lice, which are found on the seams of clothing. Scabies often presents as a more generalized pruritic rash. Diagnosis is confirmed by finding the mite in a characteristic skin burrow. Crusted (Norwegian) scabies, a rare variant consisting of infestation by thousands of mites, occurs in patients with neurologic or immunodeficiency disorders. Secondary bacterial infections and eczematous changes may complicate both pediculosis and scabies. Infestations are easily treated with use of an appropriate pediculicide or scabicide and environmental-control measures.