Methods of use in humans of probiotic bacteria of the genus Bifidobacteria for regulating the condition of human keratinous tissue to achieve cosmetic beauty benefits. Said methods include regulation, either prophylactic or therapeutic, of the cosmetic appearance of human keratinous tissue, such as human hair, skin (e.g., scalp), and nails. In another aspect, the invention provides a method of marketing a composition comprising probiotic Bifidobacteria. In one embodiment, the method comprises: (1) offering for sale a composition comprising probiotic Bifidobacteria; and (2) communicating to a potential consumer of said composition that oral administration of said composition can regulate the condition of human keratinous tissue.