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The Importance of Allergy Testing
Millions of Canadians have allergies, some of them suffering year-round and others experiencing symptoms only when seasonal pollens fill the air. Regardless of the frequency or severity, the first step in any effective allergy treatment plan is to see an allergist, a physician who specializes in treating allergies and asthma, for testing and diagnosis. Allergy tests, which have been greatly improved over the years, are now more convenient, accurate and relatively painless. Along with a patient's medical history, the results of allergy testing can confirm that symptoms are the result of allergies rather than some other cause and can identify the specific substances that trigger allergic reactions. An allergist can then determine the most appropriate and effective treatment.
How Are Allergy Tests Performed?
Allergy tests are performed using either skin tests or blood tests and should be conducted by an experienced clinician who will select the most effective testing method based on individual patient conditions.
How Do Skin Tests Work?
A drop of a suspected allergen (in a purified solution) is pricked into the surface of the skin. The test is performed on a patient's back or forearm with multiple allergens tested at once. If a patient is allergic to one of the allergens, redness and swelling will appear at the site of the prick.
How Long Does It Take to Get Skin Test Results?
One of the advantages of skin tests is that results are known quickly. Positive reactions usually appear within 15 minutes.
Is Skin Testing Painful?
Skin tests are relatively painless, as evidenced by the many young children who undergo testing with little complaint.
Do Medications Interfere With Test Results?
Some medications do interfere with skin test results. In most cases, allergists advise discontinuing the following types of medications two to four days prior to allergy skin testing: antihistamines like Benadryl®, Dimetapp®, Allegra®, Claritin®, Reactine® Aerius® and tricyclic antidepressants like Elavil®, Sinequan®, Wellbutrin®. These medications can make the skin test appear negative.
When Are Blood Tests Used?
Blood tests, known as ImmunoCap tests, often are used to test for allergies when:
· A physician advises against the discontinuation of medications that can interfere with test results or cause medical complications
· A patient suffers from severe skin conditions, such as widespread eczema or psoriasis
A patient has such a high sensitivity level to suspected allergens that any administration of those allergens might result in potentially serious side effects.
How Does the Blood Test Work?
A sample of blood is drawn and analyzed for the presence of antibodies to specific allergens.
How Long Does It Take to Get Blood Test Results?
Because the blood samples must be sent to a laboratory for analysis, the process often takes several weeks. If the results are inconclusive, the allergist must perform the test again and wait for new results.
Which Testing Method Is Best?
Allergists consider prick-puncture tests more reliable, precise, convenient and less expensive than blood tests, which do not always provide accurate and comprehensive results.
Allergy tests alone do not confirm or refute the presence of allergies. All test results, regardless of type, require a trained specialist to interpret the results in conjunction with the patient's medical history.
What Allergies Can Be Tested?
Allergy tests can be conducted for most common allergies including plant pollens, molds, dust mites, animal dander, insect stings, foods and drugs.
Who Can Be Tested for Allergies?
Adults and children of any age can be tested for allergies. However, the appropriate testing method should be chosen for very young or very old patients based on the patient's medical history and personal preferences.
Adapted from the American College of Asthma, Allergy and Immunology
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