L-cystine is a nutritional supplement. For breastmilkization of milk powder. A non-essential amino acid. It is an essential substance for the formation of skin and hair, and can facilitate the treatment of surgery and trauma. Stimulate hematopoietic function and promote white blood cell production. It has the function of promoting the oxidation and reduction of body cells, and can also be used as an additive for cosmetics, which can promote wound healing, prevent skin allergies and treat eczema.