There are two main ways to test for allergies.
The best type of allergy test, which has a higher degree of accuracy, is to perform a Skin Prick Test.
How this test is done is: An allergist or a medical doctor trained in this procedure will mark your back and then apply an extract of different allergens using a skin prick to scratch the surface of the skin. If you are allergic, your skin will show redness, possibly hives and you will experience itching at the site. This enables you to see exactly what your skin reacts to through direct contact.
Image credit: InformedHealth.org
The other test is a blood test called Immunoglobulin E RAST (Radio Immune Assay Test). This measures antibodies and immunoglobulin E levels to a particular antigen. The RAST is more expensive and at times not as accurate. The allergist cannot actually see the results on your skin.
Another test some doctors perform something called Serial End Point Titration, where they will inject different concentrations of an allergy extract into your arm and measure the redness and hives.
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