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By Mayo Clinic staffYour doctor may diagnose contact dermatitis after talking to you about your signs and symptoms and examining your skin. If the cause of your rash isn't apparent or if your rash recurs often, your doctor may recommend a patch test (contact delayed hypersensitivity allergy test).
During a patch test, small quantities of potential allergens are applied to small patches, which are then placed on your skin to check for a reaction. The patches remain on your skin for two days before being evaluated by your doctor. If you're allergic to a particular substance being tested, you develop a raised bump or a reaction limited to the skin just beneath the patch.
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- Habif TP. Contact dermatitis and patch testing. In: Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. Philadelphia, Pa.: Mosby; 2004. http://www.mdconsult.com/das/book/body/130085313-3/0/1195/18.html?tocnode=51440089&fromURL=18.html#4-u1.0-B0-323-01319-8..50006-6_242. Accessed April 6, 2009.
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