Blisters are caused by friction, trauma or internal conditions to the skin. They are formed when fluid accumulates between two layers of the skin. Diagnosis of a particular blistering disorder is usually done via biopsy in which a skin sample is taken from a blister’s edge for microscopic evaluation. Some autoimmune diseases produce blisters when antibodies attack the skin cells. Sometimes a test called immunoflourescence is performed to look for specific immune proteins that help distinguish one blistering disorders from another. Treatment for blistering disorders vary according to cause and severity.