This invention falls within the scope of sanitary and hygiene, and of antiseptic formulations in particular, including disinfectants intended for disinfection of water in swimming-pools and other artificial reservoirs, for sanitary and hygienic treatment of rooms, household equipment, furniture, household appliances and industrial equipment, as well as for disinfection of rinse and waste water. An antiseptic formulation contains nanosized particles containing both silver and silver chloride. An antiseptic formulation can additionally contain at least one amphoteric surface-active substance. In order to perform disinfection of water, nanosized particles containing silver and silver chloride are added into water at least once.