Allergy is a hypersensitivity disorder of the immune system, where our body hyper reacts to a normally harmless substance; one that does not bother most people. People who have allergies are often sensitive to more than one substance. Any substance is a potential allergen. Allergy occurs within minutes after the combination of antigen and antibody bound to a mast cell in an individual previously sensitized to the antigen. There exist people who become allergic to Non-vegetarian food, which most of us love to do. The symptoms involved includes rash, vomiting, runny nose etc.