L-Cystine Dihydrochloride is an amino acid. In the pharmaceutical industry it is used to improve hepatic function and pigmentation. In clinical nutrition L-Cysteine is used as an antioxidant agent. In the food industry it is used as an antioxidant for natural fruit juice products. It may also be used as an additive to amino acid injections to meet essential nutritional requirements in intravenous total parenteral nutrition.