Provided is a method for styling mammalian hair that includes contacting the hair with a composition that includes a poly(vinylamine-vinylformamide) copolymer and a first carrier, contacting the hair with a composition that includes a cysteine and a second carrier, and styling the hair. The method of the present invention promotes improved hair styling properties such as improved curl retention and straightness retention, e.g., under conditions of high relative humidity and temperature. The method can be used for semi-permanently straightening or curling the hair. Also provided is a method for controlling frizz by applying the copolymer and cysteine compositions.
