Process of making and using composition containing oxidation-sensitive hydrophilic active principle and maleic anhydride copolymer

A method for promoting the synthesis of the epidermal ceramides and/or for improving the barrier function of the skin, or for maintaining and/or improving the radiance of the complexion, or for preventing and/or combating roughness of the skin, or for moisturizing or treating dry skin, comprising applying to skin in need thereof a composition comprising at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its compounds and at least one maleic anhydride copolymer, said copolymer comprising one or more maleic anhydride comonomer units and one or more comonomer units selected from the group consisting of vinyl acetate, vinyl alcohol, vinylpyrrolidone, olefins comprising from 2 to 20 carbon atoms, and styrene, in a physiologically acceptable medium comprising an aqueous phase.