Cosmetic process for treating human body odor, in particular axillary odor, and optionally human perspiration, comprising: (i) a step consisting in applying to the skin a composition, in particular a cosmetic composition, comprising, in a physiologically acceptable medium, a chitosan polymer in which the amino groups are grafted with photoactive groups of azide or diazirine type of formula: wherein R' independently represents H or an acetyl group or a group -CO-L-X, the polymer containing at least one group R' = -CO-L-X, L being a linear, branched or cyclic, saturated or unsaturated divalent hydrocarbon-based group comprising from 1 to 20 carbon atoms, preferably from 2 to 10 carbon atoms, which may be interrupted with one or more non-adjacent heteroatoms chosen from sulfur, oxygen, or -NH-, -CO-, -CONH-, -COO-, -O-CO-N(Ra)-, in particular -O-CO-NH- or -N(Rb)-CO-N(Rc), in particular -NH-CO-NH-, groups, said divalent group possibly being substituted with one or more groups chosen from hydroxyl, amine, carboxylic acid, amide, cyano and (C 1 -C 4) acylamino groups, with Ra, Rb and Rc independently denoting a hydrogen atom or a linear or branched, preferably linear, C 1 -C 6 alkyl radical; X denotes a photoactive group of azide or diazirine type; n ranges from 5 to 2000; (ii) a step consisting in exposing the skin to light radiation, preferably for at least 5 seconds; the step consisting in applying light radiation being performed after or at the same time as the step consisting in applying the cosmetic composition comprising the grafted chitosan. (i) a step consisting in applying to the skin a composition, in particular a cosmetic composition, comprising, in a physiologically acceptable medium, a chitosan polymer in which the amino groups are grafted with photoactive groups of azide or diazirine type of formula: wherein R' independently represents H or an acetyl group or a group -CO-L-X, the polymer containing at least one group R' = -CO-L-X, L being a linear, branched or cyclic, saturated or unsaturated divalent hydrocarbon-based group comprising from 1 to 20 carbon atoms, preferably from 2 to 10 carbon atoms, which may be interrupted with one or more non-adjacent heteroatoms chosen from sulfur, oxygen, or -NH-, -CO-, -CONH-, -COO-, -O-CO-N(Ra)-, in particular -O-CO-NH- or -N(Rb)-CO-N(Rc), in particular -NH-CO-NH-, groups, said divalent group possibly being substituted with one or more groups chosen from hydroxyl, amine, carboxylic acid, amide, cyano and (C 1 -C 4) acylamino groups, with Ra, Rb and Rc independently denoting a hydrogen atom or a linear or branched, preferably linear, C 1 -C 6 alkyl radical; X denotes a photoactive group of azide or diazirine type; n ranges from 5 to 2000; wherein R' independently represents H or an acetyl group or a group -CO-L-X, the polymer containing at least one group R' = -CO-L-X, L being a linear, branched or cyclic, saturated or unsaturated divalent hydrocarbon-based group comprising from 1 to 20 carbon atoms, preferably from 2 to 10 carbon atoms, which may be interrupted with one or more non-adjacent heteroatoms chosen from sulfur, oxygen, or -NH-, -CO-, -CONH-, -COO-, -O-CO-N(Ra)-, in particular -O-CO-NH- or -N(Rb)-CO-N(Rc), in particular -NH-CO-NH-, groups, said divalent group possibly being substituted with one or more groups chosen from hydroxyl, amine, carboxylic acid, amide, cyano and (C 1 -C 4) acylamino groups, with Ra, Rb and Rc independently denoting a hydrogen atom or a linear or branched, preferably linear, C 1 -C 6 alkyl radical; X denotes a photoactive group of azide or diazirine type; n ranges from 5 to 2000; (ii) a step consisting in exposing the skin to light radiation, preferably for at least 5 seconds;