**1. Introduction**

Eosinophilic esophagitis (EoE) is a chronic immune/allergy mediated disease of the esophagus characterized by esophageal eosinophilia (presence of ≥15 eosinophils/high power field in at least 1 esophageal biopsy.), esophageal dysfunction (dysphagia, food impaction) and characteristic endoscopic features [1]. To establish the diagnosis, other causes of esophageal eosinophilia must be excluded. In 1989, EoE was first recognized as a distinct clinical entity by Attwood et al. [2]. Now there is an epidemic of EoE in the western world. EoE is increasingly being recognized and diagnosed in our clinical practice both in the acute and chronic settings. EoE has distinct clinical epitopes, diagnostic and treatment protocol. The epidemiology, pathogenesis, pathology, clinical feature, investigations, management and prognosis will be described in this chapter.
