Allergy skin tests, your skin is exposed to suspected allergy-causing substances (allergens) and is then observed for signs of an allergic reaction. An allergy test is an exam performed by a trained allergy specialist to determine if your body has an allergic reaction to a known substance. The exam can be in the form of a blood test, a skin test, or an elimination diet. Allergies occur when your immune system, which is your body’s natural defense, overreacts to something in your environment. Allergy testing can determine which particular pollens, molds, or other substances you’re allergic to. You may need medication to treat your allergies. Alternatively, you can try to avoid your allergy triggers.