Food allergies and food intolerance are two terms that people may use interchangeably, but they are actually to very different issues. A food allergy is a reaction caused by a protein. An allergic reaction will begin in the body upon contact or consumption with a food and can involve gastrointestinal symptoms, respiratory symptoms, and skin reactions and in some cases they can be life threatening. A food intolerance is caused by an enzyme within the food or a chemical that cannot be digested. Symptoms of a food intolerance can include diarrhea, intestinal gas, and abdominal pain, but they are not life threatening.