SUMMARY: The present invention refers to the use of hyaluronic acid in preparations for topical use - spray for oropharyngeal mucosa, aerosol for inhalation therapy and tablets soluble in the mouth for oral mucosa - aimed to the treatment and prophylaxis of pathologies which concern upper and lower respiratory tract. Hyaluronic acid topically administered accumulates completely on the irritated mucosa and, by adhering to its surface, it absorbs water thus promoting the formation of a film which hydrates and protects the same mucosae while preserving the integrity and relievng the symptoms caused by the inflammation. The other substances contained in the formulation, which act in sinergy with hyaluronic acid, are chamomile estract and n-acetylcysteine which carry out a cleansing, protective and emollient action. The quantities to be used in the formulation for the active substances are: - for hyaluronic acid sodium salt a quantity of between 0.01% and 5.0%. - for chamomile extract a quantity of between 0.01% and 5.0%. - for n-acetylcysteine a quantity of between 0.01% and 9.0%.