The signs and symptoms of a food allergy exhibited by a person depend on a number of factors, including the age of the individual, the quantity and quality of the food eaten, and the presence of other medical problems. Although the entire body may be affected, in general food allergies primarily target the gastrointestinal system, the skin, and, the least frequently, the respiratory system. Allergic symptoms therefore usually run the gamut from nausea, vomiting, and diarrhea to potentially fatal, multisystem shock. Why one organ system is the target site in one individual and not in another is still not known.

Not surprisingly, the gastrointestinal system, including the mouth and throat, is the primary target for food allergies. In fact, itching and swelling of the lips, oral mucous membranes, palate, and throat can occasionally occur as soon as the food passes through. Fortunately, such reactions are usually temporary and are not always followed by additional allergic manifestations. However, after being digested in the stomach and intestines, some offending foods will go on to provoke other GI complaints such as abdominal distention, cramps, gassi-ness, diarrhea, nausea, and vomiting.

The skin is the next most common target organ for food allergies. Typical adverse reactions include acute, and less often chronic, itchy hive reactions or severe giant hive reactions, known as angioedema. It is important to note that flare-ups of asthma, eczema, or rhinitis conditions may also occur in response to food allergy, especially in children; this connection is much less certain in adults.