Agents and method for cleaning and/or caring for damaged keratin fibers

A composition for cleaning and/or caring for keratin fibres, particularly human hair, which is free of peroxide compounds and contains at least one saturated dicarboxylic acid having 2 to 10 carbon atoms, and at least one selected amino acid of formula (VI): where X represents a hydrogen atom or a mono-or divalent cation; n represents 0, 1, 2, or 3; R1 represents a residue that is selected from an amino group, a guanidine group, a (1H-imidazol-4-yl) group, a carboxylic acid amide group CONH2, a 1H-indol-3-yl group; a thiol group SH; and a methylsulfanyl group SCH3; or at least one salt of the amino acid. The compositions also comprises at least one cleaning substance selected from surfactants, fatty alcohols, and oils. Preferably the dicarboxylic acid is present in the range of from 2 to 20 wt.%, and the amino acid is present in a total amount of 0.4 to 7.0 wt.%. The agent may also comprise a polymer of formula (I) as defined herein, such as polyvinyl pyrrolidone, and a substance of formula (III) as defined herein, such as 2-amino-3-(sulfosulfanyl)propanoic acid. The composition may be a shampoo.