Types of Allergy Tests

It used to be if you wanted to find out what you were allergic to you had to undergo a long series of tests that could take weeks or months. If you were allergic to something unusual or rare it could take years or, more commonly, you never would find out. If your allergies were seasonal, they probably disappeared before the testing clinic found an answer and you would give up on the clinic testing and go back to life as before. Much of that procedure today has been speeded up and is more straightforward but if you are being checked for allergies there will probably still be several types of tests performed.

There are three basic ways that a clinic or hospital can use to test you for allergies. The most commonly used is a skin test. This involves putting a small amount of the allergen on your skin. Allergen, by the way, is the medical term for the substance suspected of causing your allergy. Most often, the allergen is applied to your forearm but it could also be done on your back or upper arm. Then the skin in that area is irritated by pricking it with a needle or scratching the skin. This allows the substance to get under your skin. If you are allergic to it there will usually be an allergic reaction in less than 10 to 15 minutes. Usually the reaction just involves redness, itching and swelling of the skin but testers have to be careful with skin tests because in some cases the reaction may be severe and involve respiratory complications. A variation of the skin test is the intradermal allergy test. This test uses a small needle to inject the allergen just beneath the skin. Skin tests are usually used to identify things in the air that you inhale that might be causing your allergy or allergies to insect or animal bites.

A second type of allergy testing is called elimination testing. This is most often used to identify food and diet allergies. In a very controlled environment, various foods are either added or removed from your diet and your reaction is monitored. Often the food is disguised in some fashion to prevent psychological factors from interfering with the test. Sometimes if you think you are allergic to something you abnormally influence the result. Obviously, this method is very time consuming and can only be used if the reactions are relatively mild.

The third and perhaps the best method of allergy testing is the blood test. As the name implies, this involves taking a small sample of your blood and sending it off for laboratory testing. The lab procedure is complicated but basically, they will expose your blood to various allergens. If you are allergic, your blood will create what are called IgE antibodies to fight off the allergen. Depending on what kind of IgE antibodies are created and how many are created the lab can both identify your allergy and tell you how severe it is. RAST and UniCAP are the two main specific types of modern blood testing for allergies. UniCAP is almost a fully automated procedure that can check for several 100 allergens and will even assign a number from 1 to 6 to identify the severity of the allergic reaction. The major disadvantage of blood testing is it requires specialized equipment. Usually your clinic or hospital will have to mail the blood sample off and will not get results back for several weeks.