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How can you find out what you're allergic to?

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Your doctor can check to see what you’re 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. Doctors often use the T.R.U.E. test (Thin-layer Rapid Use Epicutaneous Patch 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 two days. Then the doctor takes them off to see if you've had any reactions.

You might need to come back a few more times, since some reactions could show up as many as 10 days later. You might be allergic to something that isn’t in the standard T.R.U.E. test. To figure that out, your doctor may do more patch testing. They will choose substances you might contact in your work, home, or hobbies. If you have a mild reaction in any patch test, you might need to follow up with a R.O.A.T. test (Repeat Open Application Test). It works a lot like the T.R.U.E. test, but you do it yourself. Put the suspected allergen (for example, sunscreen) on your skin during the day in the same spot over several days. This can help confirm or rule out your sensitivity. The dimethylglyoxime test looks for metal objects that have enough nickel to cause a reaction. Your doctor can test things in the office, or you can buy a kit to test jewelry and other items yourself.

SOURCES:

Handa, S. Indian Journal of Dermatology, November-December 2011.

American Academy of Allergy, Asthma and Immunolgy: "Skin Allergy."

American College of Allergy, Asthma and Immunology: "Contact Dermatitis."

Asthma and Allergy Foundation of America: "Contact Dermatits."

Santos, R. Contact Dermatitis, 2007.

Kanerva's Occupational Dermatology, Springer, 2012.

FDA: "T.R.U.E. Test: Full Prescribing Information." 

Nelson, J. Journal of Clinical and Aesthetic Dermatology, October 2010.

Medscape: “Contact Dermatitis: An Overview.”

American College of Allergy, Asthma & Immunology: “Hives (Urticaria).”

Reviewed by Stephanie S. Gardner on December 7, 2020

SOURCES:

Handa, S. Indian Journal of Dermatology, November-December 2011.

American Academy of Allergy, Asthma and Immunolgy: "Skin Allergy."

American College of Allergy, Asthma and Immunology: "Contact Dermatitis."

Asthma and Allergy Foundation of America: "Contact Dermatits."

Santos, R. Contact Dermatitis, 2007.

Kanerva's Occupational Dermatology, Springer, 2012.

FDA: "T.R.U.E. Test: Full Prescribing Information." 

Nelson, J. Journal of Clinical and Aesthetic Dermatology, October 2010.

Medscape: “Contact Dermatitis: An Overview.”

American College of Allergy, Asthma & Immunology: “Hives (Urticaria).”

Reviewed by Stephanie S. Gardner on December 7, 2020

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How long does contact dermatitis last?

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