What is a Food Allergy? A food allergy is one type of Adverse Food Reaction that is mediated by the immune system. An adverse food reaction may comprise of any symptom following the intake of a food, anywhere from minutes to days. Symptoms may be any perceptible change in how we feel and/or function. A Non-toxic food reactions can be immune- (i.e.: allergy) or non-immune-mediated. Immune-mediated reactions, or food allergies, are divided into IgE- and non-IgE reactions. A