Diagnosing<unk>  is primarily based on physical exam and medical history. In some cases doctors can establish an accurate diagnosis based on the symptoms that the patient experiences and on the rash's appearance. In the case of a single episode of<unk> , this is all that is necessary. Chronic and/or intermittent rashes which are not readily explained by history and physical exam often will benefit from further testing. Patch test A patch test (contact delayed hypersensitivity allergy test) is a commonly used examination to determine the exact cause of an<unk> . According to the American Academy of Allergy, Asthma, and Immunology, "patch testing is the gold standard for contact allergen identification". The patch test consists of applying small quantities of potential allergens to small patches and which are then placed on the skin. After two days, they are removed and if a skin reaction occurred to one of the substances applied, a raised bump will be noticeable underneath the patch. The tests are again read at 72 or 96 hours after application. Patch testing is used for patients who have chronic, recurring contact dermatitis. Other tests that may be used to diagnose contact dermatitis and rule out other potential causes of the symptoms include a skin biopsy and culture of the skin lesion.
Allergic contact dermatitis
Phototoxic tar dermatitis
Autosensitization dermatitis
Contact dermatitis
Rodent mite dermatitis
Urushiol-induced contact dermatitis
Irritant contact dermatitis
Protein contact dermatitis