biotin

1. a B vitamin (C10H16N2O3S) that aids in body growth; -- called also vitamin H and coenzyme R. It functions as a coenzyme in many carboxylation reactions.
   

Biotin binds tightly to the substance avidin, found in raw egg-whites. Rats or chick on a diet high in raw egg-white may develop skin lesions and retarded growth, which can be prevented by adding biotin to the diet.