In certain situations where an individual is experiencing an allergic reaction to an unknown substance, they may be referred to an allergy specialist who will perform specific types of tests to determine what is causing their reaction.
The most common type of testing which an allergist performs is a skin test where the surface of the skin is lightly scratched or punctured with a needle containing known allergens which cause swelling or redness around the area if the individual is allergic to that specific allergen.
However, in some cases a blood test may be given instead which is relatively more expensive but may be more beneficial in some cases to determine certain food allergies, or when an individual is taking certain medications. A blood test may also be recommended for some people with certain skin conditions such as extensive eczema.
Blood Tests
Two of the blood tests which may be performed are the 'RAST' or 'radioallergosorbent test' and the 'ELISA' or 'enzyme-linked immunosorbent assay'. Both of these tests are done by adding the suspected allergens to a small sample of blood taken from the individual and then analyzed to determine the level of certain antibodies.
The 'RAST' is the most commonly performed of the two tests and used to determine the levels of 'IgE antibodies'. If the'IgE antibodies' are at high levels, this indicates that the individual is allergic to the particular allergen which was used in the testing.
In the 'ELISA' test the levels of 'IgG antibodies' which are produced when various foods are eaten is measured to try and determine the type of foods the individual is allergic to.
The skin testing which is done to determine certain types of allergies is known to be more effective and less expensive than the blood tests however, in certain situations these may be recommended as an alternative.
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