Background: Gastroparesis is a disorder characterized by delayed gastric emptying of a meal in the absence of a mechanical gastric outlet obstruction. Idiopathic gastroparesis is at least as common as diabetic gastroparesis in most case series, and the true prevalence of gastroparesis is unknown. Results: We report here an interesting case of idiopathic gastroparesis characterized by sudden onset in a female patient. The diagnosis was confirmed by ultrasonographic study of gastric emptying and electrogastrography, by gastric endoscopy/histology, and finally by allergy tests. The disorder was found to be due to a rare cause, namely an allergic predisposition. In fact, our patient, who demonstrated an allergy to gold salts, had drunk a glass of a liqueur containing gold flakes and developed an eosinophilic aggregation in the gastric mucosa observed at gastric endoscopy/histology. The symptoms disappeared after steroid administration. Conclusion: Our experience suggests that gastric histology and close enquiry into any history of allergy may be useful diagnostic tools in cases of idiopathic gastroparesis.