Cystine is common in many foods such as eggs, meat, dairy products, and whole grains as well as skin, horns and hair.

[3] Cystine was discovered in 1810 by the English chemist William Hyde Wollaston, who called it "cystic oxide".

[4][5] In 1833, the Swedish chemist Jöns Jacob Berzelius named the amino acid "cystine".

[8][5] In 1899, cystine was first isolated from protein (horn tissue) by the Swedish chemist Karl A. H. Mörner (1855-1917).

[9] The chemical structure of cystine was determined by synthesis in 1903 by the German chemist Emil Erlenmeyer.

Typical thiols for this reaction are mercaptoethanol and dithiothreitol: Because of the facility of the thiol-disulfide exchange, the nutritional benefits and sources of cystine are identical to those for the more-common cysteine.

[14] In humans the excretion of high levels of cystine crystals can be indicative of cystinosis, a rare genetic disease.

[citation needed] Cysteine prodrugs, e.g. acetylcysteine, induce release of glutamate into the extracellular space.