Provided are a bath additive, an external preparation for skin, a reducing agent for water, a method for producing a reduced water, a reduced water, and a method for reducing an object, each of which prevents aging and provides excellent advantageous effects in health maintenance and cosmetic advantageous effects. Those described above contain: at least one type of a first alkaline agent selected from the group consisting of sodium bicarbonate, ammonium carbonate, and sodium carbonate； at least one type of a second alkaline agent selected from the group consisting of alkali metal salts or alkaline earth metal salts； and sodium borohydride as a hydrogen generating agent.
