If you or someone you love experiences symptoms such as watery eyes, nasal congestion, hives, or eczema, or has severe reactions to insect stings or after eating certain foods, you may be one of the 50 million people in the United States with allergies. The best way to find out for sure (and to start feeling better) is to see an allergist.
Your allergist may recommend allergy testing. Allergy testing has been around for more than 150 years. When combined with a physical examination and medical history, allergy testing can now confirm allergies to pollen, molds, dust mites, animal dander, insect stings, foods and some medicines.
There are many different types of allergy tests. Your allergist will determine the most appropriate test for you based on your symptoms, medical history and the allergen they suspect is causing your symptoms. With a proper diagnosis, your allergist can develop a personalized treatment plan to help you feel your best.
Skin testing is typically the first step
When identifying allergies, skin testing is often an allergist’s first choice. Here's what to expect.
Prick or scratch test: A small amount of a possible allergen is placed on your forearm or back, then pricked or scratched into the skin. You’ll usually get results in about 15 minutes. If you’re allergic, a small, red, itchy bump—like a mosquito bite—will appear where the allergen was applied.
Intradermal test: If the prick test doesn’t provide clear results, your allergist may use this method, especially for allergens like insect venom or medications. A small amount of allergen is injected just under the skin with a thin needle. Results are available in 15 minutes and can help identify allergies that the prick test might miss.
Both types of skin tests may cause slight discomfort or itching if you’re allergic to the substance tested. You’ll want to avoid antihistamines for 3-7 days before a skin test to ensure accurate results. Always check with your allergist for more specific instructions.
What about blood tests?
If skin testing isn’t an option—such as when you aren’t able to stop certain medications or have severe skin conditions—your allergist may suggest a blood test. Blood tests help identify specific allergies, but they do not measure the severity of the allergic reaction.
Oral challenges are the gold standard for food and medication allergy testing
If you’re at a low risk of having a severe allergic reaction or anaphylaxis to a food, your allergist will use one of the three different kinds of oral challenges to diagnose or rule out allergies to foods or medications. In each test, your allergist will start feeding you the suspected allergen in very small amounts. If you don’t have any significant symptoms, you will gradually receive larger and larger doses. Keep in mind that emergency medication and emergency equipment must be on hand during the oral challenge test; if you show signs of a reaction, the food challenge will be stopped. If you have no symptoms by the end of the test, your allergist will rule out an allergy.
Patch testing can determine what’s causing your rash
If you have a rash called contact dermatitis, your allergist will apply a small amount of possible allergens on patches and tape them to the skin on your back. It’s not uncommon to have 20 to 30 patches on at once — testing for allergies to latex, cosmetics, medications, fragrances, creams, detergents, hair dyes, metals and resins. After a few days, your allergist will remove the patches; irritated skin at the patch site may mean you have an allergy.
Use caution with at-home food sensitivity test kits
There are methods of allergy testing that are not useful or effective, or that may lead to inaccurate diagnosis and treatment. Home food sensitivity test kits might show reactions to foods you are tolerating without any problem and can cause you to unnecessarily take foods out of your diet, increasing your chance of developing an allergy to a food you previously tolerated. If you aren’t sure about a particular test or method, talk with your allergist.
Test results alone do not diagnose allergies
If the results of skin and blood allergy tests are not clear or are inconsistent with the patient’s medical history, allergists rely on their training and experience along with a patient’s medical history and a physical examination—not test results—to make the final diagnosis.
Once diagnosed, your allergist will sit down with you and discuss your treatment options.
Know that allergies can change over time
While there are no limitations to the frequency of allergy testing, retesting should rarely be necessary within a three-year period. Exceptions include young children with negative skin tests or older children and adults with negative skin tests. If you’re having persistent or worsening allergy symptoms, retesting may be repeated one year later.
For more information on allergy testing, or to find an allergist in your area, use the ACAAI allergist locator tool.
