This study prospectively enrolls patients with suspected and previously diagnosed Eosinophilic Esophagitis seen at Lurie Children’s to better understand clinical subtypes, molecular biomarkers, drivers of treatment response, and ultimately pathogenesis. The study collects clinical information such as demographics, medical and atopic history, family history, and lab work/allergy testing. At the time of endoscopy, validated symptom and quality of life questionnaires are completed by the family, and endoscopic scoring is recorded by an EoE-specialized endoscopist. Histologic scoring is performed by a GI pathologist. Additional biopsies and blood are collected for studies in the laboratory of Dr. Joshua Wechsler to understand the role of mast cells in driving endoscopic and histologic changes, along with molecular predictors and mediators of diet elimination responses.