Food allergy
People often think that they have an allergy to the food. In fact, only about 1% of adults and 3% of children have clinically proven allergic reactions to food. This difference between the prevalence of clinically proven food allergy and the public's perception of the problem is due primarily to misinterpreting food intolerance as food allergy. Food allergy is an abnormal response to food that is triggered by a specific reaction in the immune system and expressed by certain, often characteristic, symptoms. Food intolerance also is an abnormal response to food, and its symptoms can resemble those of food allergy. Food intolerance, however, is far more prevalent, occurs in a variety of diseases, and is triggered by several different mechanisms that are distinct from the immunological reaction responsible for food allergy. People who have food allergies must identify and prevent them because, although usually mild and not severe, these reactions can cause devastating illness and, in rare instances, be fatal.

A sugar that occurs naturally in fruits and honey. Fructose has 4 calories per gram.