The present invention relates to a process for treating keratin fibers comprising the steps of: applying onto the keratin fibers a composition comprising at least one amino acid except for cystein, basic arginine and basic lysine； then placing the keratin fibers in an occlusive space； and then heating the keratin fibers, wherein the composition contains neither a reducing agent nor a source of carbonate ions of the formula: wherein X is a group selected from the group consisting of O-, OH, NH2, O-OH, and O-COO-. The present invention also relates to the composition itself and a kit to be used for the above process.
