Tests Used to Diagnose Allergies

By Spader, Catherine, RN

If you often suffer from allergy symptoms—runny nose, itching, rashes, or wheezing—allergy testing can help you find out exactly what is causing your symptoms. Today’s tests are more accurate and convenient and the most important step toward designing a treatment plan to control and even eliminate your symptoms.

Why Should I See My Doctor?

Symptoms of different allergies and conditions can be very similar. For the most accurate diagnosis and the most effective treatment plan, your doctor or an allergist can perform a complete evaluation and a series of tests.

You can help your doctor by:   

  • Compiling a medical history. Be prepared to provide detailed information about your symptoms, when you notice them the most, and any personal and family history of other allergy-related conditions including eczema and asthma.

  • Keeping track of your symptoms. Your doctor may ask you to keep a record of your symptoms including when and where they occur, how severe they are, how long they last and what you were doing or eating at the time. The symptom log is particularly helpful for if your doctor suspects that you have a food allergy.

Allergy Tests Your Doctor May Order

After completing your medical history and physical exam, your doctor may order certain types of allergy testing. There is no single test that can diagnose allergies and what substances cause your symptoms. Your doctor may need to perform multiple tests including:

  • Skin testing. Skin testing involves putting a drop of an allergen on the skin—usually the back or forearm—and then pricking the area with a needle so a small amount of the substance gets under your skin. If you are allergic to the allergen, you will develop a bump or redness at the site. Since the skin prick testing is not completely accurate, your doctor may order another skin test in which a small amount of allergen is injected just under your skin. These patch and intradermal tests also involve watching for a reaction after injecting an allergen into the skin. 

  • Blood tests. Blood tests involve drawing a blood sample and testing it for IgE antibodies. As part of an allergic reaction, your body produces certain IgE antibodies. Your doctor may also order a radioallergosorbent test (RAST). This blood test helps identify what causes your allergic reaction. Although a safer option for testing food allergies, RAST test are not as accurate for testing food allergies.

  • Provocation tests. Provocation or challenge testing involves exposing you to small amounts of allergen while you are carefully watched for signs of a reaction. For example, you will eat or inhale small but increasing amounts of different substances that might cause your allergies.

  • Elimination test. An elimination test is used see if you have a food allergy. During this test, you eliminate suspect foods from your diet for a week or more. Your doctor will tell you how to add the foods back into your diet, usually one at a time, while watching for signs of an allergic reaction.

You should understand that elimination testing is not always accurate. It can also be dangerous, especially if you have had a severe reaction to a certain food. You should not try an elimination diet by yourself without talking to your doctor.

Medical Reviewer: William C. Lloyd III, MD, FACS Last Annual Review Date: Dec. 15, 2013 Copyright: © Copyright 2013 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

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