Eosinophils are one of the components of white blood cells produced in the bone marrow and are one of the cells that play a role in promoting inflammation, especially allergic inflammatory reactions. Therefore, large quantities of eosin can accumulate in tissues such as the esophagus, stomach, small intestine and sometimes in the blood when such individuals are exposed to the allergen.

Eosinophilic esophagitis (EoE) is an immune-mediated clinical condition presenting with symptoms of esophageal dysfunction and esophageal eosinophilia. Because of the presence of eosinophilia and response to PPI therapy, GERD and PPI-REE have become the most common alternative diagnoses for EoE.

Proton pump inhibitor-responsive eosinophilia should be suspected if esophageal symptoms and eosinophil histological findings demonstrate a symptomatic and histological response to proton pump inhibitors.