The investigators seek to assess the efficacy of removing cow's milk from an EoE patient's diet. This will be determined by esophageal inflammation and clinical and histological response to the milk elimination treatment.

The dietary approach is based on the hypothesis that food antigen(s) trigger eosinophilic inflammation and clinical and histological remission can be induced by identifying and excluding the causative food antigen(s). It is believed that eliminating causative food antigen(s) target the cause and thus induces long term remission.

This process is difficult as it requires multiple, invasive endoscopies and introduces the possibility of iatrogenic effects such as nutrient deficiency due to simultaneous multiple food eliminations. In addition, patient compliance may be compromised, both intentionally and unintentionally as many families report the elimination process to be both confusing and frustrating.

This prospective study eliminating only cow's milk proteins, which are a common cause of esophageal inflammation in patients with eosinophilic esophagitis, will assess the histological response in a cohort of children receiving care at Lurie Children's.

Inclusion Criteria:

• Patients aged 1-18
• Patients who meet the criteria for diagnosis of EoE with ≥15 eosinophils per high power field and who had been previously treated with an adequate dose of PPI for 6-8 weeks or had a normal 24 hour ph probe study will be recruited from the patients seen by one of the physicians in the EoE clinic at Lurie Children's and other participating centers
• Patients who agree to cow's milk elimination diet as their treatment of EoE

Exclusion Criteria:

• Patients who started on oral or swallowed steroids (prior use of steroids that was discontinued more than two months prior to enrollment does not constitute an exclusion criterion)
• Patients who are unable to tolerate the cow's milk elimination diet
• Patients with concurrent eosinophilic gastroenteritis or eosinophilic colitis

The sample size was determined based on the one-proportion non-inferiority test. The investigators recruited 54 subjects throughout the recruitment period.