A cosmetic agent for treating keratin fibers is provided herein. The cosmetic agent includes, in a cosmetically acceptable carrier, in relation to the total weight of the cosmetic agent, from about 0.001 to about 10 wt. % of at least one protein which has a content of glutamic acid and/or aspartic acid of from about 10 to about 60%, in relation to the total content of all amino acids of the protein. The cosmetic agent further includes, in a cosmetically acceptable carrier, in relation to the total weight of the cosmetic agent, from about 0.01 to about 10 wt. % of at least one salt which includes at least one divalent cation, and/or of at least one salt which includes at least one trivalent cation.