Allergy Testing- Allergy/Immunology, Dermatology

What are allergies?

Allergies occur when our immune system, which is the defense mechanism of our body against foreign bodies, overreacts to an allergen (pollen, dust).  As a result we can develop symptoms like sneezing, runny nose, itchy, watery eyes and blocked sinuses. Exposure to allergens can also trigger acute exacerbations in asthmatic patients. Although medications will help to control the symptoms, it is also important to identify the substances causing the allergy so that appropriate precautions can be taken to minimize exposure to them.

What is allergy testing?

Allergy testing is an exam performed to determine if our body has an allergic response to a known substance.  Allergy testing is performed by an allergist who is a physician specialized in diagnosis and treatment of asthma and other allergic diseases.

How to prepare for allergy testing?

Your doctor will take a detailed family history, ask questions about your lifestyle and will gather other relevant information before the allergy testing.

Certain medications would need to be stopped because they can interfere with the results of the allergy tests. Talk to your doctor to understand more.

How allergy testing is performed?

Allergy tests include blood tests and skin tests. An elimination diet is recommended for testing food allergies.

1) Skin Tests

Three Skin tests are tried:

Scratch Test – The 1st test is called as the scratch test. For this test a liquid containing the allergen is placed in a special device, which lightly punctures the allergen into the skins surface. Swelling., elevation, localized tenderness or itchiness of the skin over the test site indicates that the patient has an allergy to the allergen being tested.

Intra-Dermal Test – In this test, a tiny amount of the allergen is injected into the dermis layer of the skin and the physician monitors if the patient develops an allergic reaction over the test site

Patch Test- In this test adhesive patches loaded with allergens re placed on the patients skin. They are then reviewed after 48 hours and again at 48-72 hours after application. Irritated skin at the patch site may indicate allergy.

Risks for Skin Test - In some rare cases, skin tests can result in a severe allergic reaction. Ideally, it is better to perform skin allergy tests at a clinic or hospital where appropriate emergency medication and equipment are available.

2) Blood Tests - In blood tests, physicians look for specific antibodies, which fight allergens. Since blood tests are expensive, they are not routinely done. They are useful in patients who are not suitable to undergo skin allergy tests.

3) Elimination Diet – This is done to test for food allergies. Certain foods are removed from the patients diet and added back later. The reaction of the patient to the different foods helps determine which foods are causing problems.



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