Graying of Hair Produced by Ingestion of Phenylthiocarbamide

(1) After being placed on a stock diet and given phenylthiocarbamide solution as the sole source of fluid, with one exception 23 black or black hooded rats showed definite graying, some as early as 27 days and all within 58 days. (2) Approximately 83 days after the phenylthiocarbamide solution was replaced by tap water, five rats that had shown marked graying turned completely black again. (3) The experiments showed that graying may result from a positive factor in the diet, a poison, as well as from a deficiency of some factor.