Introduction: Eosinophilic gastroenteritis (EG) is a rare condition of unclear etiology. It is characterized by peripheral eosinophilia, eosinophilic infiltration of the bowel to a variable extent, and gastrointestinal symptoms. The pathophysiology of EG may be related to allergic disorders, but it is not completely understood. Case Report: An 83-year-old female presented with brownish, watery diarrhea and dull abdominal pain for a period of 2 weeks. The patient reported 7-8 episodes of diarrhea in a day, not associated with blood or mucous. She denied any vomiting, fever, recent travel, sick contact, or antibiotic exposure. Physical examination was unremarkable except for mild abdominal tenderness in the left lower quadrant. Stool studies were negative for occult blood, Clostridium difficile, bacterial infection, ova, and parasites. Laboratory studies showed white blood cell count of 21k/mm3 and absolute eosinophil count of 4,180 cells/mm3 (19%). Colonoscopy showed diverticulosis of the colon, and biopsy was consistent with marked eosinophilic infiltration of the colonic and terminal ileal mucosa. Total IgE level was elevated to 159 Ku/L. These features led to the diagnosis of EG. Discussion: EG is an uncommon cause of gastroenteritis. Symptoms of EG depend upon the layer of bowel affected by eosinophilic infiltration. Mucosal involvement results in nausea, vomiting, non-specific abdominal pain, diarrhea, and malabsorption. Muscle layer involvement causes symptoms of intestinal obstruction, whereas subserosal infiltration causes eosinophilic ascites. It is very important to rule out intestinal parasitic infections. Irritable bowel syndrome can present with similar clinical presentation, and is one of the important differential diagnosis. Currently, treatment of EG is empiric and based upon severity of disease. Patients with mild and sporadic symptoms can be managed with reassurance and expectant observation, whereas those with severe GI symptoms and malabsorption should be treated with systemic glucocorticoids. Sodium cromolyn, ketotifen, and elimination diet may be useful in patients with history of allergic disorders. Surgical intervention is reserved for patients with obstructive symptoms.Figure 1