Allergy Skin Testing

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Allergy skin tests are performed to confirm whether or not you are allergic to a specific substance (allergen). Testing typically takes 20 to 30 minutes and can be performed on your arms or back. Allergy skin tests can help your doctor diagnose several allergic conditions, including:

  • Hay fever
  • Food allergies
  • Allergic asthma
  • Eczema

Patients of all ages can benefit from allergy skin testing, including infants. However, your doctor may suggest you not undergo testing if you:

  • Have had a severe (potentially life-threatening) allergic reaction to a substance
  • Have certain skin conditions that can cause test results to be unreliable
  • Take certain antihistamines, antidepressants or other medicines that can interfere with results
  • Have severe eczema or other skin conditions. The affected areas of skin may be so large that there may not be enough “clear” skin to effectively perform the test.

Allergy skin tests are typically most reliable for diagnosing allergies to airborne substances, like pollen, dust mites and animal dander. Allergy skin testing may also be helpful for identifying food allergies. However, because food allergies can be complex, you may need more procedures or tests to confirm results.

There are three types of skin tests:

  • Skin Prick Test. This test is typically used to diagnose allergies to foods, dust mites, pet dander, mold and pollen. Adults usually receive this test on the forearm. Children may be tested on the upper back. A nurse will apply the allergens to your skin using lancets (needles). You should have no bleeding, and experience nothing more than mild, momentary discomfort. The nurse observes your skin after about 15 minutes. If you are allergic, you’ll develop a red, raised, itchy bump at the test site, similar to a mosquito bite.
  • Skin Injection Test. Your doctor may recommend this test to help identify allergies to penicillin or insect venom. During the test, a tiny amount of allergen extract is injected into the skin on your arm. The test site is observed for signs of an allergic reaction after about 15 minutes.
  • Patch Test. A patch containing an allergen is placed on your arm or back. This test can identify a delayed response to a specific allergen. It is typically performed to see whether or not a specific substance is irritating the skin (contact dermatitis). During the test, your skin is exposed to 20 to 30 allergen extracts, including medicines, latex, hair dyes, metals and fragrances. You must wear the patches for 48 hours. You should avoid bathing or other physical activities that cause sweating. The patches will be removed at the doctor’s office. Irritation at the patch site may be a sign of an allergy.

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