Causes

The blisters occur because of a malfunction in your immune system.

Your body's immune system normally produces antibodies to fight bacteria, viruses or other potentially harmful foreign substances. For reasons that are not clear, the body may develop an antibody to a particular tissue in your body.

In bullous pemphigoid, the immune system produces antibodies to the fibers that connect the outer layer of skin (epidermis) and the next layer of skin (dermis). These antibodies trigger inflammation that produces the blisters and itching of bullous pemphigoid.