Allergy tests are medical procedures performed to measure the body’s immune response to specific allergy triggers (also known as allergens). If you have an allergy, your immune system overreacts and produces an abundance of chemicals that trigger an allergic reaction. Healthcare providers perform allergy tests to determine what substance, in particular, is causing your immune system to react excessively.   Substances that trigger allergic reactions are many and varied. The most common allergens are mold, pollen, pet dander, bug bites, latex, and food-related allergens (such as milk, soy, and peanuts).