A preparation and dispensing system prepares and dispenses a personalized composition from N reserves (501-502) of active compounds (A1-A2), N being an integer greater than or equal to 1, which is accurate, quick, easy to implement, hygienic and economical. The system comprises a pneumatic-pressure generator (200) connected to a pressure distributor (300) comprising N pressure changeover switches (301-306), each one having at least one inlet (I1) connected to the pressure generator, one inlet (I2) connected to atmospheric pressure and an outlet (311-316) connected to an inlet of a reserve of active compound.