The cosmetic composition for cosmetically treating parts of the body comprising keratin-containing material includes one or more conventional cosmetic auxiliary ingredients and a cosmetically active compound, which is prepared by covalently bonding peptide linker molecules with known organic cosmetic effector molecules. The peptidic linker group is a peptide group, preferably with from 2 to 15 amino acids, which has binding specificity for keratin-containing material. The organic cosmetic effector molecules have dyeing, care-imparting, conditioning, protective, hardening, softening, repairing and/or strengthening properties for keratin-containing material. The method of cosmetically treating parts of the body that include keratin-containing material, for example a method of dyeing hair, includes applying the above-described cosmetic composition to the parts of the body.