Infectious Disease: Bedbugs, Lice, and Mites.

Bedbugs, mites, and scabies are ectoparasites that commonly affect humans. Bedbugs ( Cimex species) were once rare in the United States but are now common. They cause intensely pruritic lesions on areas of exposed skin. The bites are highly allergenic and can cause asthma exacerbations or anaphylaxis. Management of bedbug bites involves symptomatic relief of itching and dealing with patient anxiety. Identification and elimination of infestation are most important. Another ectoparasite of concern is lice ( Pediculus and Pthirus species), which causes head, body, and pubic infestations. Patients can experience hypersensitivity to the saliva of lice, but such symptoms often do not develop until several weeks after infestation. Diagnosis involves identification of nits (ie, eggs) or lice on the skin or hair. Several pediculicides are used for management but wet combing without use of pediculicides may be more effective. A third common ectoparasitic infestation, scabies (ie, infestation with the mite Sarcoptes scabiei ), affects 5% of the world's population. Patients present with pruritic lesions in skin folds, finger webs, and areas in which clothing is tight. The diagnosis can be confirmed with dermatoscopy or microscopy. Management involves use of permethrin cream, oral ivermectin, or benzyl benzoate.