What is allergy testing? How and where can I get a test done?

Information about Allergy Testing

Allergy testing is a method of finding the cause of an allergic reaction in people facing allergic reactions. An allergy test is also used to determine whether the symptoms are genuinely reactions of the immune system to an allergen (which involves release of antibodies and histamine) or simply mimic allergies (allergy like symptoms without antibody and histamine production).


How and where is an allergy test done?

Qualified doctors perform allergy testing in specialized clinics. Initially a doctor examines the patient and gathers a detailed history of events that could have led to the reaction. This is important because the type of test to be performed depends upon the allergy symptoms you exhibit. There are three main types of allergy tests –


  1. Skin tests
  2. Blood tests
  3. and Elimination or food challenge allergy test.

Majority of doctors prefer the skin test initially as it is less expensive and more specific than the blood test.


Allergy Testing - Skin tests – These are done if the doctor suspects that your allergy is caused by airborne triggers like dust and pollen or by allergens that come in contact with your skin like detergents and perfumes. Skin allergy testing is of three types. Each of these allergy test is unique in its own way and has different accuracy levels.

  • Scratch (Prick) Tests: are the most common skin allergy test. As the name suggests, the procedure involves pricking or scratching the arm of a patient with a needle or sterile blade. This allows the drops of suspected allergens placed on different marked spots on the forearm to penetrate into the skin. Allergic symptoms like redness, scratching or swelling are checked after a reaction time of 30 minutes. The spot where these symptoms are observed points out the problematic allergen.
  • Patch tests: are run when a doctor suspects a particular allergen to be the likely cause of your allergic reaction. This allergy testing involves applying a patch with a small amount of allergen on the skin. After 2 days, the patch is removed and signs of allergic reaction are noted. If there is an area of rash or redness on the skin covered by the patch, or you have a hypersensitive allergic reaction to the patch, then the test is said to be positive for that particular allergen.
  • Intradermal tests: These are more accurate than the other 2 skin allergy tests and are usually done as follow-up tests to ascertain the allergen. In this test, the doctor injects a small amount of suspected allergen under the skin (which gave a positive reaction in the scratch or patch test) with a sterile needle. Results are noted after 20 minutes.

Allergy Testing - Blood test – Blood allergy test is recommended in patients who are extremely sensitive to an allergen, to an extent that slightest of contact like in the skin test can send them into anaphylaxis (a hyper-reactive allergic reaction). In this test, a sample of your blood is drawn and sent to a special laboratory for a RAST test (Radio Allergo Sorbent Test) or CAP-RAST.


The allergy test measures the amount of specific Immunoglobulin E antibodies (IgE) in your blood to various environmental and food allergens. For example, a person with allergy for house dust mite will have an elevated level of the immune system’s response - house dust mite IgE. The result is graded on a scale of 0 to 6 depending on the level of this IgE in the blood.


Elimination or Food Challenge Allergy Test – This allergy test is performed in people who are suspected to have allergies to specific food substances. Though skin tests are capable of detecting food allergies, there are some food allergens that cannot be found even in the skin tests. So food tests are done to find which specific allergen in your food is giving you an allergy.


Elimination allergy test involves excluding the food items form a patient’s diet, which he suspects of giving him an allergy. The doctor asks the patient to carefully observe his allergy symptoms and note if they reduce with exclusion of the specific foodstuff. After 2 weeks, the excluded food is re-introduced in his diet and the patient is observed under the doctor’s supervision for allergic reactions.


The food challenge allergy test is a bit risky and involves giving the patient food that he may be allergic to. If the test is positive, the patient shows allergic signs like rash and redness, but at times can suffer from an anaphylactic shock, which could prove fatal. That is why food challenge test is done under supervision in the hospital with facilities to tackle anaphylactic emergencies.


This article will help you understand the fundamental approach to allergy testing. Allergy testing can also be using Complementary and alternative medicine methods, which has been discussed in another article.


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