Eosinophilic esophagitis (EoE) is a chronic, immune-mediated disease, induced by food allergens, clinically characterized by symptoms of esophageal dysfunction. Pathologically there is a predominant eosinophilic inflammation. This disease is relatively new, and its definitions have evolved over time. Its prevalence and incidence are increasing and causes clinical problems both in children and adults. Its symptoms include food impaction, dysphagia, symptoms that resemble gastroesophageal reflux, abdominal pain, and vomiting. It can also have extra-digestive symptoms such as rhinosinusitis, chronic cough, recurrent croup and hoarseness. EoE can be associated with other atopic conditions, such as asthma, eczema and food allergies. The diagnosis is made by the analysis of endoscopic biopsies (> 15 eosinophils per high power field). Proton pump inhibitors (PPIs) are currently accepted as a treatment for EoE. The clinical and pathological improvement with the use PPIs ceased to be a criterion to define Esophageal eosinophilia responsive to PPIs as a differential diagnosis, since this condition is currently considered within the EoE spectrum. There are three main treatment approaches for EoE: diet, drugs and dilation. Its diagnosis and early treatment are key to avoid or delay its complications, such as stenosis and severe esophageal dysfunction.