Allergies are hypersensitivities that involve reactions of the immune system to substances that do not cause reactions in most people. The substances that trigger the reaction are called allergens.
Allergies affect as many as 40% of people worldwide and have become increasingly common in recent decades. Examples of potential allergens include plants, insect venoms, dander from pets, mold spores, materials, foods, and drugs. They can trigger diverse symptoms that range from mild to severe.
Several types of tests can be used to determine whether a person is allergic to a specific substance. Because there are diverse kinds of allergens, appropriate testing is important to identify and manage allergies.
Allergy testing is usually diagnostic, meaning that it is done after someone has had signs of an allergic reaction. By reviewing the symptoms, a primary care physician or allergist can prescribe and perform tests for the most likely allergens. When both past reactions and testing indicate an allergy, it can enable treatment or avoidance of the allergen.
It’s uncommon to do broad screening for allergies in people who haven’t had any prior allergic reaction symptoms because some tests may have potential false positives that show sensitivity to a substance when no real allergy exists.
In people who have received treatment for allergies, testing may be used to monitor their response or to determine if they still have hypersensitivity to a substance.
Getting allergy test results
Allergy test results are usually reviewed with the doctor and in many cases with a specialist known as an allergist. Test results alone often aren’t enough to demonstrate an allergy. Instead, they are typically considered together with past patient reactions.
Depending on the test results and patient history, more than one test may be used to either confirm or rule out an allergy.
Types of Allergy Tests
Tests of the blood and skin are the standard ways of identifying potential hypersensitivities.
Allergen-specific immunoglobulin E (IgE) testing is the most common blood allergy test. IgE is a type of protein known as an antibody that is associated with allergic reactions. Certain types of IgE are related to specific allergens, and elevated levels can reflect a possible hypersensitivity.
The skin prick test is the most frequent allergy skin test. It involves placing a small drop of a potential allergen on your skin and then lightly pricking you with a tiny needle to allow the substance to get just beneath your skin. An intradermal skin test is similar but uses a larger needle to inject the substance deeper into your skin.
For these tests, doctors usually choose which allergen(s) to test for based on a review of your symptoms. When necessary, they can test for more than one allergen at the same time.
Often, no further tests are needed to determine if a person has an allergy. However, additional allergy tests, described below, may be used in certain circumstances.