The authors report the case study of a 16-year old boy who presented with cyclic vomiting syndrome. His main clinical symptoms had been unpredictable sudden-onset vomiting episodes interrupting long episodes of full health lasting for several months since the patient was a toddler. Histological results of the upper tract endoscopy showed eosinophil gastroenteritis with long-existing, undetected cow milk allergy as the likely underlying reason. The patient became symptomless following the elimination of cow milk from his diet. The symptoms did not recur following a cow milk load test carried out half a year later, and the patient continues to be symptomless after more than one-year of continuous cow milk consumption. In this paper, the authors would like to highlight the importance of EG int the differential diagnosis of any chronic, recidive gastrointestinal symptoms and discuss the likely underlying causes of EG in paediatrics.