When allergic patient is exposed to an allergen, it can trigger the disease. SPT can make diagnosis of allergic trigger factors. Small amount of allergen is instilled in the skin and the site is observed after 10-15 minutes. If there is swelling and redness at that site it confirms the causal allergen. Patient should not be on many medicines including antiallergic medicine, antidepressant etc.
Skin prick test. A skin prick test, also called a puncture or scratch test, checks for immediate allergic reactions to as many as 40 different substances at once. This test is usually done to identify allergies to pollen, mold, pet dander, dust mites and foods. In adults, the test is usually done on the forearm.
Accuracy of Skin Prick Tests. SPTs seldom produce "false negatives" (erroneous results indicating that you are not allergic to a food, even though you really are). Negative results almost always mean that you are not allergic to a food. Positive tests, however, are not always accurate.