Most common cause of erythema multiforme?

Ans. a (Herpes simplex). (Ref. Harrison's, Principles of Internal Medicine, 16the d., pg 112)ERYTHEMA MULTIFORME# A vesiculobullous disease.# Pink red macules & papules with dusky violet colour or petechiae center which later becomes vesicles is clue to diagnosis (centrifugal spread).# "Target/iris" lesions--characteristic.# Preferred sites--distal extremities, mucous membrane.# Hemorrhagic crusts of lips characteristic (d/d - herpes simplex, pemphigus vulgaris, paraneoplastic pemphigoid)# Lesions resolve in 3-6 weeks