Eosinophilic esophagitis (EOS) is a condition of eosinophil infiltration in the esophagus causing clinical symptoms. This is a new disease that has only really received attention in the last 20 years. The first case described by Landres in the medical literature in 1978 was a case of a patient initially diagnosed with achalasia, then discovered thickening of the muscular layer in the esophagus and histopathological results showed eosinophil infiltration.