Inclusion Criteria:  Pediatric patient, ages 5-18 years old, who will undergo esophagogastroduodenoscopy with biopsies at Children's Memorial Hermann Hospital, as part of the standard of care in the evaluation of EoE Signed informed consent by a parent or legal guardian Signed assent form by the child/adolescent subjects 7-18 years of age  Exclusion Criteria:  Past medical history of active asthma, active allergic rhinitis, inflammatory bowel disease (IBD), parasitic infection, hay fever and any exposure to smoking (including secondhand smoke) because these disorders are known to affect the FeNO levels Active respiratory tract infections at the time of FeNO evaluation because this can affect the result of the FeNO as well Asthma questionnaire and/or Spirometry test consistent with asthma