Skin Prick Test

Skin testing is one of the most common and reliable ways to test for environmental and food allergies. To diagnose a food allergy, your allergist may use a skin prick test (SPT) to measure the presence of IgE antibodies for the suspect food. SPTs are inexpensive, produce immediate results, and can be performed in the doctor’s office.

During this test, the allergist places a drop of solution containing the food allergen on your forearm or back. (When testing fruits or vegetables, fresh food may be used instead of a solution.) Using a small plastic probe or needle, the doctor gently pricks or scratches the skin to allow a tiny amount of the solution to enter just below the surface. The SPT is generally not painful and there is no bleeding. The scratching on the surface of the skin feels similar to a fingernail scratch.

Depending on your case history, you may be tested for one food or several. Results usually appear within 30 minutes. Positive results are indicated by a wheal – a raised white bump surrounded by a small circle of itchy red skin. In general, a large wheal is more likely to indicate a true food allergy, but size is not always an accurate predictor. If no wheal appears, it is unlikely that you are allergic to the test food.