There are two types of skin tests, percutaneous (also known as prick, puncture or scratch testing) and intracutaneous (intradermal) testing. During a percutaneous test, the skin is pricked or scratched to introduce a tiny drop of a suspected allergen (in a purified solution) into the surface of the skin. The test is performed on a patient's back or forearm with multiple allergens tested at once. If a patient is allergic to one of the allergens, a small, itchy red spot that looks a lot like a mosquito bite will appear at the site of the test.If a percutaneous test is inconclusive, a physician may perform an intracutaneous test. During an intracutaneous test, small amounts of purified allergen solution are injected into the patient's arm or forearm. Because the allergen is injected below the surface of the skin, it is a more sensitive test that may produce a false positive result.