How Allergy Skin Tests Work
Skin testing also sets off an allergic reaction, but only on your skin. Your doctor places a tiny amount of the allergy trigger on your body, usually on your back or forearm, and then pricks or scratches the skin underneath.
If nothing happens, you're not allergic to that trigger. If you are, you'll get a small, raised bump that itches like a mosquito bite. That's how your doctor can tell what's causing your symptoms.
What to Expect
Skin tests are accurate, but they're not perfect. It's important to work with an allergist who has a lot of experience with allergy testing.
Skin Testing Side Effects
If your body reacts to the allergy trigger, you'll have swelling and some itchiness at the site of the skin prick. These symptoms usually start within 15 minutes and fade within 30 minutes. Rarely, some people have a delayed reaction 24 to 48 hours later.
More serious allergic reactions are very rare. To be safe, doctors always do allergy testing in an office where they can watch you.
After skin testing, your doctor can tailor your treatment and give you advice on what to do next. You may need:
More testing. If results weren't clear, your doctor may want to do some more checks. Some people need blood tests or "challenge testing," in which you breathe in or take by mouth small amounts of the allergy trigger.
Changes at home. Once you know what you're allergic to, you can take steps to protect yourself. For instance, if dust mites are the problem, you can wrap your mattress in an allergy-proof cover to keep them out.