Bullous pemphigoid is a potentially life-threatening condition that causes large fluid-filled blisters to form on parts of the body such as the lower abdomen, armpits or upper thighs, according to Mayo Clinic. The condition occurs most often in patients over the age of 60.
Bullous pemphigoid occurs when the body has an abnormal immune response and attacks the thin layer of tissue below the skin, according to Mayo Clinic. Certain medications may trigger the condition, though the exact reason for the immune response that leads to bullous pemphigoid is unknown, as of 2015. Treatment typically requires the use of corticosteroids to suppress the immune system.