A retrospective study of patients with pemphigus vulgaris, drug eruptions, psoriasis, and normal controls was undertaken in an attempt to determine whether a significant difference in drug exposure and/or drug allergy existed between the various groups. A statistically significant difference in drug exposure was found between pemphigus vulgaris and drug eruption patients, as compared with psoriatics and normal patients. Representative case reports and some possible mechanisms for the induction or exacerbation of pemphigus patients is described and discussed.