pure encapsulations biotin 8 mg | b vitamin supplement for stress relief, hair, skin, and nail strengthening, metabolism, glucose support, and nervous system* | 120 capsules pure encapsulations biotin is a water-soluble b vitamin that is an essential co-factor for a number of metabolic carboxylation reactions involved in metabolism. recent studies have expanded biotin's metabolic role, claiming that the vitamin maintains healthy genetic expression of the many enzymes for which it is a cofactor. clinical studies have indicated that biotin may adjust the cellular arrangement of the nail bed, helping to reinforce the keratin structure, promote strength and thickness, and reduce splitting.