Biotin No Help for Infantile Seborrheic Dermatitis: A double-blind cross-over trial of biotin given by mouth in the treatment of seborrhoeic dermatitis of infancy did not show a statistically significant advantage of biotin over placebo. Oral use of biotin in seborrhoeic dermatitis of infancy: a controlled trial. Keipert JA. Med J Aust. 1976 Apr 17;1(16):584-5

Biotin Helped Hoofs of Cattle: in large DB PC study. J Dairy Sci. 2000 Feb;83(2):338-44. It also has a small positive effect on horses.