Allergy testing involves having a skin or blood test to find out what substance, or allergen, may trigger an allergic response in a person. Skin tests are usually done because they are rapid, reliable, and generally more accurate and less expensive than blood tests, but either type of test may be used. Along with allergy testing, for adults, a screening test for asthma will be performed since 40% of people that have allergies will likely develop asthma.
A small amount of a suspected allergen is placed on or below the skin to see if a reaction develops. There are two types we do in our office:
Skin prick test
This test is done by placing a drop of a solution containing a possible allergen on the skin, and a series of needle pricks allows the solution to enter the skin. If the skin develops a red, raised itchy area (called a wheal), it usually means that the person is allergic to that allergen. This is called a positive reaction.
During this test, a small amount of the allergen solution is injected into the skin. An intradermal allergy test may be done when a substance does not cause a reaction in the skin prick test but is still suspected as an allergen for that person. The prick test and the intradermal test are used together to determine what you are allergic to and how intense the allergy is.