This assembly is of the type including: a vessel (4) for containing liquid, the vessel (4) having a neck (14)； a dispensing dropper end fitting (6) disposed at the end of the neck (14)； and a cap (8) for closing the vessel (4), provided to be screwed onto the neck (14). In a preferred embodiment, the cap (8) and the neck (14) have safety element preventing the cap (8) from being unscrewed simply by applying an unscrewing torque, and allowing the cap (8) to be unscrewed when an additional action is applied together with the torque for unscrewing the cap (8).
