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Tests and diagnosis

By Mayo Clinic staff


Image showing patch testing on the back
Patch testing

Your 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.

  1. Weston WL, et al. Overview of dermatitis. Accessed April 2, 2009.
  2. Cohen DE, et al. Allergic contact dermatitis. In: Wolff K, et al. Fitzpatrick's Dermatology in General Medicine. 7th ed. New York, N.Y.: The McGraw-Hill Companies; 2008. Accessed April 6, 2009.
  3. 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. Accessed April 6, 2009.
  4. Wetter DA, et al. Patch test results from the Mayo Clinic Contact Dermatitis Group, 1998-2000. Journal of the American Academy of Dermatology. 2005;53:416.
  5. Kaplan LA. Exposure to radiation from the sun. In: Auerbach PS. Wilderness Medicine. 5th ed. Philadelphia, Pa.: Mosby; 2007. Accessed April 6, 2009.


July 31, 2009

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