Bullous pemphigoid appears as a sometimes-itchy rash of large blisters that come and go on either normal or inflamed skin, often in the creases of the arms and legs.
It's considered an autoimmune disorder but thought to be harmless. Certain medications, such as furosemide (to reduce water retention) and enalapril (to treat high blood pressure or heart failure), may trigger the condition.
Treatment generally includes oral or topical corticosteroids.
Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50