The safest way to test for an allergic reaction is through a skin prick test, supervised by a qualified allergist. In this test, small amounts of allergens are introduced into the skin using a needle-like device. Whether a person is allergic is determined by observing skin reactions, such as redness or swelling at the test site. This method is relatively quick and considered safe, as it allows for immediate observation of reactions. Blood tests can also be performed to measure specific IgE antibodies but may take longer to process.