A one-way valve for the recontamination-protected repeated discharge of a flowable material from a container of a preferably reducible volume contains a valve seat which consists of a rigid plastic material and which is arranged in the container neck and comprises a base body which rests on the inner wall of the container neck and contains at least one through hole, and a projection which extends in axial direction of the container neck towards the exit opening. The valve seat has arranged thereabove an elastic seal which comprises an annular section covering the at least one through hole, and a sleeve-like section which surrounds the projection at a radial distance with the exception of its end section which in the closed state of the one-way valve rests in the exit opening on the end section of the projection. A sterilization element of silver or of another metal having an oligodynamic action may be arranged in the intermediate space between the projection of the valve seat and the elastic seal. The application of pressure to the contents of the container has the effect that the annular section of the seal releases the at least one through hole of the valve seat, the end section of the sleeve-like part of the seal exiting from the exit opening and releasing the same. The seal will then return into the initial state. The contents of the container is safely sealed against the ingress of contaminants.