When the immune system responds to a substance that is harmless to most people, it causes an allergic reaction. These substances, called allergens, include pollen, dust mites, pet dander, mold, certain foods, insect venom, and some medications. Allergy testing helps allergists identify which substances may trigger these responses. Several testing methods are available, and each one serves a different purpose. Here’s more information on allergy testing methods to support your allergy management plan:
Skin Tests
For people with allergies, the immune system mistakenly identifies an allergen as a threat and produces antibodies known as immunoglobulin E (IgE). These antibodies prompt cells to release histamine and other chemicals that can cause sneezing, itching, hives, or swelling. Skin tests are the most common allergy testing methods allergists use to evaluate possible allergies. They involve exposing a small area of skin to specific allergens and observing the reaction.
Patch Test
A patch test evaluates delayed allergic reactions, such as contact dermatitis. An allergist applies small amounts of potential allergens to adhesive patches placed on the skin, usually on the back. Common test substances include nickel, fragrances, preservatives, and hair dyes. The patient wears the patches for about 48 hours while avoiding bathing and heavy sweating. After removal, the allergist examines the skin for irritation or rash.
Skin Prick Test
The skin prick test, also called a scratch test, checks for immediate allergic reactions. An allergist places a drop of liquid containing a possible allergen on the forearm or back. A small, sterile device then lightly pricks the skin’s surface to let the allergen enter. Several allergens are usually tested at once, and results typically appear within 15 to 20 minutes. A raised, red bump called a wheal may indicate sensitivity to a specific substance.
Intradermal Skin Test
An allergist may recommend an intradermal skin test when skin prick test results are unclear, but this method may be more sensitive than a skin prick test. A thin needle is used to inject a small amount of allergen just beneath the skin’s surface. Allergists often use it to evaluate allergies to insect venom or certain medications, such as penicillin. Results typically appear within 15 to 20 minutes.
Blood Test
A blood test is an option for people who cannot undergo skin testing, such as those with severe eczema or who take medications that interfere with skin test results. An allergist or technician draws a small blood sample from a vein in the arm. The sample is sent to a laboratory for analysis, where lab technicians measure IgE antibody levels that respond to specific allergens. Elevated levels may suggest sensitivity to a substance. Blood tests do not expose the patient directly to allergens; however, they may cost more than skin tests.
Oral Challenge Test
An oral challenge test evaluates food allergies, and an allergist may recommend it when skin or blood test results are inconclusive. It may also be appropriate when a patient’s symptoms do not match their test results or to determine whether a child has outgrown a food allergy. During the test, the patient eats a very small amount of the suspected food, and the amount gradually increases over several hours.
Medical staff closely monitor the patient for signs of a reaction. This oral test takes place in a medical setting with emergency equipment available, as food allergy reactions can be life-threatening. Testing ends if symptoms appear, confirming the allergen.
Try Allergy Testing
Allergy testing shows how the immune system responds to specific substances. Skin tests, blood tests, and oral challenge tests each offer a different approach to identifying potential allergens. An allergist can review your symptoms and current medications to determine which allergy tests may suit your needs. If you experience recurring symptoms that may relate to allergies, schedule an appointment with an allergist to discuss testing options.
