Biotin is one of the minor B vitamins whose function has not been entirely evaluated. It is found in most multivitamin preparations, but only in minute quantities. Foods containing biotin include eggs and organ meats legumes, cauliflower, broccoli, and mushrooms. How biotin works on brittle nails and cracked hooves is unknown. It appears to be safe, with no side effects and is available without a prescription from health-food stores and pharmacies. However, since its effectiveness is dependent on very high doses to work, it would be prudent to check with one’s physician prior to starting biotin treatment.