We report the case of a young female patient, admitted for a recent ascites of unknown origin. The acute onset was with colicky abdominal pain and peritoneal effusion, which led to the suspicion of perforated ulcer. A diagnostic laparoscopy was performed which showed free peritoneal fluid and normal abdominal viscera. At upper gastro-intestinal endoscopy, performed a few days later, patchy erythema in the antral region and duodenal edema were revealed. Duodenal biopsies showed marked eosinophilic infiltration. The ascitic fluid was straw coloured, sterile with 90% eosinophils. Eosinophilic gastroenteritis was suspected, but differential diagnosis required the exclusion of migrant parasites. The stool exams were negative but serology for Toxocara antibodies was positive. The treatment with albendazole (Zentel 400 mg twice a day for 5 days) led to the disappearance of signs and symptoms. The eosinophilic infiltrate of the gut was absent in duodenal biopsies taken two months later.