A skin prick test (SPT) is a common test for food allergies. Food allergy symptoms happen when your body reacts to a food and makes an antibody called IgE (immunoglobulin E). Allergy doctors use SPTs as a quick and reliable way to check for IgE antibodies for certain foods.

During an SPT, your doctor will put a drop of liquid with a specific food allergen on your arm or back. They will then prick or scratch your skin through each drop using a small needle. This lets a tiny amount of the food allergen go just under your skin.

Your doctor may test a single food allergen or several foods at once. Results should appear within 15 to 20 minutes. Your allergist will review results with you and help you understand what it means.

The test is considered POSITIVE if a wheal (sounds like “wheel”) appears on your skin. Wheals are raised, white bumps inside a small circle of itchy, red skin. (If you have dark skin, the wheal may be difficult to see, so you may need additional tests.)

In general, a large wheal is more likely to indicate a true food allergy, but the size of the wheal is not always an accurate predictor. If no wheal appears, it is unlikely that you are allergic to the test food. Having a negative test means it is unlikely you have a food allergy.

Accuracy of Skin Prick Tests

SPTs are not always accurate. If you take an antihistamine (like Benadryl® or Zyrtec®) before the SPT, you may get the wrong results. Your allergy doctor will often ask you to stop taking antihistamines before your SPT. If stopping your medication for a short time will make your symptoms worse, your doctor may choose to perform a blood test.

A positive test plus a history of food allergy symptoms is needed for a diagnosis of food allergy, which is why it is critical to have a medical professional interpret these results.

Other Proven Testing Methods: