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What is Involved in an Allergy Test?

Article Details
  • Written By: Carol Francois
  • Edited By: Bronwyn Harris
  • Last Modified Date: 04 July 2018
  • Copyright Protected:
    2003-2018
    Conjecture Corporation
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An allergy test is used to diagnose food and environmental allergies. There are two types of allergy tests: the skin, or prick, test and the blood test. A doctor or nurse practitioner should administer these tests. An allergy is a disorder of the immune system, causing it to overreact to harmless substances.

The skin test is the most common of all the allergy testing methods. The patient completes a questionnaire to help determine the food, airborne and contact allergies they have noticed. The questionnaire is usually quite detailed, asking for the number of allergic reactions, intensity, and frequency in the last 12 to 18 months.

The doctor or nurse practitioner reviews the questionnaire and discusses the responses with the patient. A list of specific allergens is identified for testing. These allergens are based on known inter-relationships and similarities. For example, there is no need to test for both oranges and lemons, as they below to the same family.

Depending on the number of allergens included in the allergy test, the actual test pricks may be done on the forearms or back. The surface of the skin is wiped with an alcohol solution. The doctor then takes a sterile needle and dips it into the allergen. The skin is broken and the allergen is introduced into the body. This process is repeated for every allergen they are testing.

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A map or grid is created to keep track of the location each allergen was applied for diagnostic purposes. The patient moves to a waiting room and is observed for ten to 15 minutes. During this time, medical staff monitors the patient, just in case there is an extreme allergic reaction. A sudden drop in blood pressure, the appearance of hives, or the development of anaphylactic shock are all severe reactions and require immediate medical assistance.

At the end of the waiting period, the doctor returns and compares the map to the skin. If you have an allergy, a welt will appear where the allergen was introduced. The skin will be very itchy, red, and sensitive to the touch.

The blood test is much less common allergy test. It is more expensive, and there are some questions about the validity of the results. In this test, several vials of the patient’s blood are drawn. The total IgE or immunoglobulin E levels in the blood are tested to determine if the person has an overactive immune system.

The issue with this test stem from the fact that no specific allergens are identified. The process simply verifies if the body has an overactive immune system. Several diseases and syndromes can create the same effect in the body, but are not related to allergies at all.

If you are going to have an allergy test, purchase an antihistamine beforehand and have it ready to take as soon as the test is over. Keep in mind that the body will continue to react to the allergen for several days after the test.

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