Eosinophilic gastroenteritis (EG) is composed of a group of uncommon and enigmatic disorders that affect the stomach and small intestine. Involvement of the esophagus and large intestine is occasionally seen. The salient feature of this disease is infiltration of areas of the gut with eosinophils, a type of white blood cell produced in bone marrow. Eosinophilia (increased numbers of eosinophils in the blood) is also a common finding, present in over 50% of patients. The diagnosis of EG is confirmed by biopsy of the stomach or small intestine, usually by the nasogastric route.