What to expect during an allergy skin test
Q: I’ve been told I may need to have an allergy skin test to determine what I’m allergic to. Are these safe?
A: During allergy skin testing, your skin is exposed to suspected allergy-causing substances (allergens) and is then observed for signs of an allergic reaction. Along with your medical history, allergy tests may be able to confirm whether a particular substance you touch, breathe or eat is causing symptoms.
Information from allergy tests may help your doctor develop an allergy treatment plan that includes allergen avoidance, medications or allergy shots (immunotherapy).
Allergy skin tests are widely used to help diagnose allergic conditions, including hay fever (allergic rhinitis), allergic asthma, dermatitis (eczema), food allergies, penicillin allergy and insect venom allergy.
In general, allergy skin tests are reliable for diagnosing allergies to airborne substances, such as pollen, pet dander and dust mites. Skin testing may help diagnose food allergies. But because food allergies can be complex, you may need additional tests or procedures.
Skin testing is usually done at a doctor’s office. A nurse generally administers the test, and a doctor interprets the results. Typically, this test takes about 20 to 40 minutes. Some tests detect immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests detect delayed allergic reactions, which develop over a period of several days.
Before you leave your doctor’s office, you’ll know the results of a skin prick test or an intradermal test. A patch test may take several days or more to produce results.
A positive skin test means that you may be allergic to a particular substance. Bigger wheels usually indicate a greater degree of sensitivity. A negative skin test means that you probably aren’t allergic to a particular allergen.
Keep in mind that skin tests and blood allergy tests aren’t always accurate. They sometimes indicate an allergy when there isn’t one, a false positive, or skin testing may not trigger a reaction when you’re exposed to something that you are allergic to, a false negative. You may react differently to the same test performed on different occasions. Or you may react positively to a substance during a test but not react to it in everyday life.
Your allergy treatment plan may include medications, immunotherapy, changes to your work or home environment or dietary changes. Ask your doctor to explain anything about your diagnosis or treatment that you don’t understand. With test results that identify your allergens and a treatment plan to help you take control, you’ll be able to reduce or eliminate allergy signs and symptoms.