Eosinophilic esophagitis is an uncommon pathology that generally affects children with a history of allergies and intrinsic asthma. We present a clinical case of eosinophilic esophagitis in a 16-year-old boy with upper dysphagia for solids since childhood. The analytical study showed only a repeat serum eosinophilia. Barium transit disclosed a reduction in caliber of the whole esophagus. Functional esophageal tests with pH monitoring and manometry were normal. Endoscopy showed a small-diameter esophagus and fibrosis with a very friable mucosa. The histological study of the esophageal biopsies revealed a full thickness major eosinophil infiltration of the esophagus. These findings suggest a differential diagnosis with a great variety of pathologies that can cause similar lesions in the esophagus, especially between primary eosinophilic esophagitis and eosinophilic esophagitis secondary to gastro-esophageal reflux disease (GERD). We implemented medical treatment with oral corticoids and total suppression of allergens from the diet, and the patient was asymptomatic.