In their cross-sectional study, Hurrel, Genta and Dellon examined esophageal biopsy samples that were taken from 2008 to 2010 as part of a large US pathology database. Using a temperate climate (as defined by the Köppen–Geiger climate class) as a reference, the researchers found that esophageal eosinophilia was more likely in a cold climate or an arid climate than in a tropical climate. They believe that geographical and climate patterns can be used to help identify candidate antigens for investigation.