Abstract: A milk-protein hydrolyzate consisting of a mixture of peptides and free amino acids having proliferation activating property on human cutaneous cells but not having antigenicity of the milk-protein may be obtained by enzymatic hydrolysis of milk protein. The peptides of the hydrolyzate have molecular weights less than 1000 daltons, and the hydrolyzate has a free aromatic amino acid/total aromatic amino acid ratio of at least 90%. Fractionation of the milk protein hydrolyzate yields a fraction consisting of a mixture of peptides. The fraction has a proliferation activating property on human cutaneous cells but does not have the antigenicity of the milk protein. The fraction contains aromatic amino acids in an amount of less than 5% by weight of total amino acids. Both the hydrolyzate and the fraction can be formulated into cosmetic compositions for application to the hair and skin.