Biotin (also known as vitamin B7 or vitamin H) is a water-soluble vitamin that acts as an essential cofactor for carboxylase enzymes in multiple metabolic pathways. Today it is part of numerous formulations of supplements for its beneficial benefits on hair and nail growth. This new review systematically analyzes the scientific literature on case reports and randomized clinical trials on the efficacy of biotin in the growth and strengthening of nails and hair. All cases have shown a clinical improvement following integration with biotin, particularly in those with biotin (acquired or hereditary) deficiency and related diseases, such as fragile nail syndrome or non-combable hair.

Patel, Deepa P., Shane M. Swink, and Leslie Castelo-Soccio. “A Review of the Use of Biotin for Hair Loss.” Skin Appendage Disorders 3.3 (2017): 166-169.