Intradermal Allergy Testing
What is an Intradermal Allergy Test?
An intradermal allergy test involves injecting a small amount of allergen under the skin. This is typically done after a scratch test if that scratch test has proven inconclusive. Intradermal allergy tests can test a for a variety of allergies including insect sting allergies and drug allergies.
Using a very thin needle, the allergist injects a diluted form of the allergen just below the skin. The section of skin is then closely observed for at least 15 minutes. If the skin reacts to the injection and develops a red, itchy wheal, this indicates that the body has responded to the allergen with an allergy antibody, confirming an allergy. Generally speaking, the larger the reaction in the skin, the higher the patient’s sensitivity to the allergen is.
Skin testing should only be conducted by trained medical professionals who understand the risks involved and can carefully monitor symptoms and reactions.
Intradermal Test vs. Allergy Scratch Test
Both allergy scratch tests and intradermal tests are commonly used in the diagnostic process when diagnosing allergies. An allergy scratch test is usually used as a preliminary test. If the results of a skin test are inconclusive, the allergist will then typically conduct an intradermal test.
In either scenario, an allergist may also recommend blood testing if additional information is needed to confirm or refine a diagnosis.
What to Expect During an Intradermal Allergy Test
It is likely that your allergist will test for a number of different allergens during an intradermal test. It can take about 15 minutes total to place all of the allergens on the skin.
Adults typically receive the injections on the arm, while children will receive them on the back. You can expect some mild discomfort during the procedure. If an allergic response occurs, you may also experience itching and aggravation at the site.
Each site must be observed for at least 15 minutes after application of the allergen. Your allergist will be looking for a skin reaction, but also monitoring you for more severe reactions. All in, intradermal testing takes anywhere from 30 to 45 minutes and is an outpatient procedure.
Are Intradermal Allergy Tests Accurate?
Allergy skin tests in general are very reliable techniques for diagnosing allergies. While not 100 percent accurate, intradermal allergy tests are still widely considered one of the most accurate methods for diagnosing allergies.
You can have a false positive with an intradermal allergy test, or you may react to a substance during testing, but not in the regular course of your life. In any scenario in which results are inconclusive, your allergist may also recommend blood testing.