Signs of aging of the skin and/or mucous membranes are prevented and/or reduced, and the activity of the proteolytic enzymes of the stratum corneum are stimulated as well, by administering to an individual in need of such treatment, a cosmetic/pharmaceutical composition which comprises a thus effective amount of at least one hydroxylated urea compound having the following formula (I): in which: the radicals R1, R2, R3 and R4, which may be identical or different, are each a hydrogen atom, a C1-C4 alkyl radical or a C2-C6 hydroxyalkyl radical which can contain from 1 to 5 hydroxyl groups, wherein at least one of the R1 to R4 radicals represents a hydroxyalkyl radical, or salt, solvate or isomer thereof, formulated into a physiologically acceptable medium therefor.