Contact dermatitis is diagnosed through a physical examination by a doctor and a careful evaluation of symptoms. To identify the trigger substance, especially if allergic contact dermatitis is suspected, a patch test (also known as an allergy test) is frequently performed. During this test, adhesive patches containing potential allergens are placed on the skin. After a few days, the patches are removed, and the skin is checked for an allergic reaction to determine which substances cause sensitivity. In rare cases, a skin biopsy may be performed to confirm the cause of the rash or to rule out other skin conditions. A biopsy involves examining a skin tissue sample under a microscope. Additionally, a skin culture may be taken if a skin infection is suspected.