The present invention concerns compositions for rinsing the nasal cavity and the sinus cavities for curative or prophylactic treatments of acute and/or chronic rhinitis, and acute and chronic sinusitis, comprising: sodium chloride and/or potassium chloride； quercetin, and at least one active agent of the polyphenolic group chosen from the compounds: quercetin-4'-glucoside, 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone, protocatechuic acid； and wherein the quercetin is in the anhydrous form with an approximate molecular mass of 302 g/mol, or in the form of quercetin hydrate with an approximate molecular mass of 320 g/mol, or in the form of quercetin dihydrate with an approximate molecular mass of 338 g/mol. The present invention also relates to method for preparing these compositions and to the method for treating acute and chronic rhinosinusitis using these compositions.
