The investigators seek to assess esophageal inflammation or lack of it in response to treatment with a novel non-invasive method that would measure eosinophil-associated inflammatory mediators in the blood and urine to determine the presence of active Eosinophilic Esophagitis. For these purposes, the investigators will correlate esophageal inflammatory mediators measured in blood and urine with histological findings identified on esophageal mucosal biopsies. Additionally, biopsies associated mediators will be assessed relative to clinical phenotype and outcome.

The diagnosis, assessment of recurrence of inflammation, response to treatment and remission in EoE are all currently based on histological evaluation of upper endoscopic pinch esophageal biopsies. Obtaining biopsies for histological evaluation by this procedure is both invasive and expensive. The purpose of our longitudinal prospective study is to evaluate and quantify a panel of novel non-invasive eosinophilic inflammatory biomarkers in the blood and urine of subjects with EoE and compare their presence and levels with the presence or absence of measures of inflammation in esophageal biopsies. While evaluation of esophageal biopsies with 15 or more eosinophils per high power field is the gold standard for diagnosis of EoE, novel predictors of clinical outcome remain unclear. The objective is to identify one or more sensitive and specific non-invasive biomarkers that could be used to monitor esophageal inflammation, and identify novel tissue-based markers that identify phenotype and outcome. This would eliminate the need for invasive serial surveillance endoscopies for the purpose of evaluating for recurrence of inflammation or response to standard therapy since symptoms alone do not adequately correlate with either the presence or absence of disease activity (inflammation) in the esophagus of patients with EoE.

Inclusion Criteria:

• Patient ages 1-18 undergoing upper endoscopy for suspected esophageal disease or esophageal inflammation or has histologically confirmed esophageal inflammation may be included in this study

Exclusion Criteria:

• Patients with a history or current diagnosis of esophageal malignancy or subjects with graft versus host disease will be excluded from the study.
• Patients that are considered at high risk for biopsies at the discretion of the child's physician and/or the researcher
• Patients with known bleeding disorders or patients with illnesses where bleeding would pose a threat to their health
• Diagnosis other than Eosinophilic Esophagitis (EoE) i.e. Inflammatory Bowel Disease (IBD), Gastroesophageal Reflux Disease (GERD)

Any patient undergoing a clinically indicated upper endoscopy with biopsy for suspected esophageal inflammation or esophageal disease, or who has histologically confirmed esophageal inflammation may be asked to enroll in this study. The investigators plan to recruit subjects for two years, and enroll up to 150 patients. The patients with a confirmed diagnosis of EoE will be followed in the study for two years after enrollment.