Food protein-induced enterocolitis syndrome (FPIES) is a rare food allergy that affects the gastrointestinal tract, primarily in infants and young children. It is caused by an immune reaction to certain proteins found in food, leading to inflammation and damage to the intestines. Common triggers include cow's milk, soy, rice, and oats. Symptoms typically occur within hours of ingesting the offending food and may include severe vomiting, diarrhea, dehydration, and lethargy.