The invention concerns a dosing unit for a powder dispenser comprising two dosing chambers (2, 3) each chamber comprising: one upstream inlet (21, 31) and one downstream outlet (22, 32), an upstream means (23, 33) for opening and closing the inlet, a downstream means (24, 34) for opening and closing the outlet, the upstream means (23, 33) closing the inlet (21, 31) when the downstream means (24, 34) opens the outlet (22, 32) and reciprocally, wherein the upstream means (23) of the first chamber closes the first chamber (2) when the upstream means (33) of the second chamber opens the second chamber (3) and reciprocally.
