Abstract: The present invention is directed to compositions, devices, and methods for non-irritatively treating and preventing mucositis, such as chronic rhinosinusitis (CRS). Some aspects of the invention concern compositions comprising or consisting essentially of sodium phosphate buffer (e.g., sodium phosphate dibasic and sodium phosphate monobasic) and calcium carbonate; mucoadministration devices and kits containing such compositions; and methods for treating or preventing mucositis conditions such as CRS, comprising mucoadministering a composition of the invention to a subject in need thereof.