"Our hair is as much as 14 percent L-cysteine, an amino acid commonly used to make meat flavorings and to elasticize dough in commercial baking. How commonly? Enough to merit debate among scholars of Jewish dietary law, or kashrut. "Human hair, while not particularly appetizing, is Kosher," states Rabbi Zushe Blech, the author of Kosher Food Production, on Kashrut.com "There is no 'guck' factor," Blech maintained, in an e-mail. Dissolving hair in hydrochloric acid, which creates the L-cysteine, renders it unrecognizable and sterile."