A dosing unit includes a piston movable along a first axis in a cavity of a casing, provided with an inlet and with an outlet for a product to be dosed, and in a further cavity of the casing, connected to and substantially coaxial with the cavity and provided with a further outlet for cleaning and/or sterilizing fluids. The casing includes an internal tubular element in which the cavity is made and a covering element that externally envelops the internal tubular element and extends from an end of the internal tubular element in such a way as to form the further cavity.