Food allergy occurs most frequently in children from birth to age three.
After age five, most children have outgrown these reactions. Individuals allergic to peanuts or shrimp, however, generally seem not to outgrow their allergy. Not all reactions occurring after food ingestion are caused by food allergy. For example, unpleasant symptoms after food ingestion may be caused by contamination of foods with toxins or preservatives or result from intrinsic ingredients in the food with pharmacological properties. Sometimes a metabolic deficiency of the person ingesting the food can be the cause of symptoms.