A cosmetically acceptable composition comprising about 0.01 to about 40 weight percent, based on polymer solids, of a stable solution of a cationic copolymer composed of about 1 to about 99 mole percent diallyl-N,N-disubstituted ammonium halide and about 99 to about 1 mole percent N-vinylpyrollidone, wherein the solution as a RSV of about 0.4 to about 10 dL/g, methods of preparing the composition and methods of using the composition to treat keratinous substrates such as hair, skin and nails.