Eosinophilic esophagitis (EoE) is defined by symptoms related to esophageal dysfunction, persistent esophageal eosinophilia, and exclusion of other etiologies that may be contributing to the condition. EoE is different from erosive esophagitis. In children, symptoms vary by age groups, such as feeding disorders in 2 year olds; vomiting in 8 year olds; and abdominal pain, dysphagia, and/or food impaction in adolescents. Most adults present with dysphagia, food impaction, heartburn, or chest pain. Common endoscopic features in adults with EoE include linear furrows (creases that orient longitudinally), mucosal rings (esophageal "trachealization"), small-caliber esophagus, white plaques or exudates (which are microabscesses of eosinophils), and strictures. Children often present with similar endoscopic features, yet one-third of pediatric patients with EoE have a normal result in an endoscopic examination. Histologic features of EoE include increased intramucosal eosinophils in the esophagus (≥15 eosinophils per high power field), without similar findings in the stomach or duodenum. There also may be eosinophilic microabscesses. In addition to evidence of mast cell activation, mucosa from patients with EoE have increased levels of interleukin 5; supporting eosinophilia; and upregulation of gene expression of eotaxin-3, a chemokine important in eosinophil migration. The majority of patients have evidence of either aeroallergen and/or food sensitization. Dietary therapy is considered first-line therapy for patients with EoE because it is inexpensive and effective, without requiring pharmacologic therapy. Removal of food antigens has been shown to improve symptoms in patients with EoE. Topical corticosteroids improve esophageal eosinophilia and symptoms, and have become the criterion standard of pharmacotherapy.