Allergy Skin Test
An allergy skin test exposes your skin to suspected allergens to identify the specific substances causing your immune system to overreact.
What is an allergy skin test?
An allergy skin test identifies the cause of an allergic reaction by exposing the skin to specific allergens. These tests primarily check for Type 1 hypersensitivity, which is responsible for common allergies to dust mites, pollen, food, and animal dander. Symptoms of these reactions can range from mild rashes to life-threatening anaphylactic shock.
What is it used for?
The test is used to diagnose specific allergies, allowing your provider to create an effective treatment plan, which may include avoidance strategies, medication, or lifestyle changes.
What happens during an allergy skin test?
Tests are typically performed by an allergist or dermatologist using one of the following methods:
- Scratch test (skin prick test): Small drops of allergens are placed on the skin, which is then lightly pricked. A positive reaction appears as a wheal (a small red bump) within 15 to 20 minutes.
- Intradermal test: A small amount of allergen is injected just below the skin surface. This is often used for insect stings or penicillin allergies if a scratch test is negative.
- Patch test: Patches containing allergens are applied to the skin for 48 to 96 hours to check for delayed reactions like contact dermatitis.
Preparation and Risks
You may need to stop taking antihistamines or certain antidepressants before the test. For patch tests, avoid heavy sun exposure for two weeks prior. While the test is generally safe, it must be performed in a medical office equipped to handle rare cases of anaphylactic shock. The most common side effect is localized itching or redness.
What do the results mean?
- Positive: Red bumps or swelling indicate you are likely allergic to the substance.
- Negative: No reaction suggests you are likely not allergic.
If diagnosed, your provider will guide you on managing your condition. If you are at risk for anaphylactic shock, you must carry an emergency epinephrine auto-injector at all times.