An increased coexistence of gastroesophageal reflux disease (GERD) and chronic rhinosinusitis (CRS) has been reported in epidemiologic and register studies, and reflux has been shown more frequently in patients with CRS in studies using esophagus pH manometry compared to participants without CRS. A discussion is ongoing about whether there might be an association between these two diseases and, if so, whether the association is causal.