Tests and diagnosis

By Mayo Clinic Staff


The key to successful treatment of contact dermatitis is identifying what's causing your symptoms and figuring out whether you have the irritant or allergic type. Doctors rely on these main steps to determine the cause:

  • A thorough medical history and physical exam. Your doctor may be able to diagnose contact dermatitis and identify its cause by talking to you about your signs and symptoms, questioning you to uncover clues about the culprit, and examining your skin to note the pattern and intensity of your reaction.
  • A patch test. Your doctor may recommend a patch test (contact delayed hypersensitivity allergy test) to see if you're allergic to something. This test can be useful if the cause of your rash isn't apparent or if your rash recurs often.

    You may be asked to avoid certain medications and sun tanning your back for a week or two before the test.

    During a patch test, small amounts of potential allergens are applied to adhesive patches, which are then placed on your skin. The patches remain on your skin for two days, during which time you'll need to keep your back dry.

    Your doctor then checks for a skin reaction under the patches and determines whether further testing is needed. Often, people react to more than one substance.

July 16, 2014