Different persons are allergic to different substances. Allergy testing is necessary to determine the substances to which a person is allergic. There are a number of methods of allergy testing. The methods generally used are the skin tests, elimination-type tests, and the radioallergosorbent tests (RAST).
There are several types of skin tests. In the scratch test, a tiny amount of suspected allergy-causing substances is placed on the skin. The skin is then scratched or pierced so that the allergen is introduced under the skin surface. The skin is then observed closely for signs of a reaction, usually in the form of swelling and redness of the site. Results are available within about 20 minutes, and several suspected allergens can be simultaneously tested by this method of allergy testing.
Falling into the category of skin tests, another method of allergy testing involves injection of a small amount of allergen under the surface of the skin and watching for a reaction at the site. Skin tests are suitable for respiratory allergies, a penicillin allergy, insect bite allergies, and food testing.
Elimination-type tests are useful for testing food allergies.
In this method of allergy testing, the suspected allergy-causing foods are eliminated from the diet for several weeks and then gradually re-introduced one at a time. At the same time, the person is continuously observed for signs of an allergic reaction. If a person is under the impression that he/she is allergic to a certain food, it is better to take a double-blind test to determine if this is true.
In a double-blind test, suspected foods and placebos (harmless substances) are provided in a disguised form and the person being tested and the provider are both unaware of whether the substance tested in that session is the placebo or the food substance. Only a third party knows the identity of the substances and identifies them with some sort of code. This test may need several sessions if more than one substance is under investigation.
The RAST is a laboratory test performed on blood. This method of allergy testing looks for the amount of specific IgE antibodies in the blood, which are present if there is a true allergic reaction.
Among other types of allergy testing are immunoglobulin measurements and the blood cell differential or absolute eosinophil count, in which rise in eosinophils can indicate allergy presence. Provocation or challenge allergy testing involves exposure to the suspected allergen under controlled circumstances. As it may provoke severe allergic reactions, it should only be performed by a doctor.
Before you are subjected to any type of allergy testing, the doctor will inquire about your illnesses, social and emotional conditions, work, entertainment, lifestyle, foods, and eating habits.
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