skin disorders
Overview of Hypersensitivity and Reactive Skin Disorders
Diagnosis
A doctor's examination Sometimes a biopsy The diagnosis of most hypersensitivity and reactive skin disorders that cause a rash is based on the appearance of the rash. The cause of a rash often cannot be determined by blood tests, so they are not usually done. However, persistent rashes, particularly those that do not respond to treatment, may lead the doctor to do a Biopsy in which a small piece of the skin affected by the rash is removed with a blade for examination under a microscope. 