A food allergy is an abnormal response by the body's immune system to a particular food. Symptoms can include itching in the mouth, vomiting, hives, and asthma. In some cases, the reaction can be so severe that it causes serious illness, or even death. Sometimes people suspect a food allergy, when they are really experiencing another type of reaction called "food intolerance." Food allergy treatment usually involves avoiding the food that triggers the reaction.