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Allergies Health Center

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Skin Allergies and Contact Dermatitis: The Basics

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Tests for Allergic Contact Dermatitis

Your doctor can check to see what you might be reacting to, but finding the exact cause may be hard. Skin tests can only show what you're sensitive to. They can't tell what touched your skin in a specific spot on a specific day.

Skin doctors often use the TRUE test. It's a pre-packaged set of three panels that your doctor will stick to your back. Each is smaller than a dollar bill and has 12 patches with samples of possible allergens. You wear them for 2 days, and then he'll take them off and check to see if you've had any reactions. You might need to come back a few more times, too, since some reactions could show up as many as 10 days later.

Since you might be allergic to something that's not in the standard TRUE test, you doctor may also want to do more patch testing of substances related to your work, home, or hobbies.

If you've had a mild reaction in any patch test, you might need to follow up with a ROAT, or repeat open application test. It's a similar idea, but you do the test instead of your doctor. You'll put the suspected allergen, such as your sunscreen, on your skin several times in the same spot over several days. This can help confirm or rule out your sensitivity.

The dimethylglyoxime test helps find metal objects that have enough nickel to cause a reaction. Your skin doctor can test things in the office, or you can buy a kit to test jewelry and other items yourself.


The best treatment is prevention. Find out what causes your rash and avoid it. You may need to wear gloves to protect your skin.

When you have a reaction, try to ease the symptoms and prevent an infection. Don't scratch, even though that's a hard urge to resist. Over-the-counter products and home remedies can help relieve the itching and stop the swelling:

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