Food allergy is an allergic disease caused by the hypersensitivity of the immune system food. Food allergy can be caused by various allergic reactions but 90% of allergic responses to food are caused by cow's milk, soy, eggs, wheat, peanuts, tree nuts, fish, and shellfish. Food Allergy can cause itching, swelling of the tongue, vomiting, diarrhea, hives, trouble breathing, or low blood pressure in a person and usually occurs within minutes to several hours of exposure.