Benign familial chronic pemphigus, or Hailey-Hailey disease, is a rare hereditary condition characterized by development of blisters at sites of friction such as the neck, axillae and groin. Contact sensitivity to topical medications is reported to be common and routine patch testing has been strongly advocated. We report a case of Hailey-Hailey disease in a 43-year-old veterinary surgeon who presented with an acute exacerbation of his disease caused by herpes simplex virus type 1 (HSV). Patch testing was carried out to exclude a coexistent contact dermatitis and was complicated by severe local blistering. We are reporting this case to remind clinicians that HSV is a recognized cause of exacerbations of this disease and to warn that patch testing is not without hazard.