Is Cystine vegan?

Q: Is Cystine vegan?

Cystine is not reliably vegan. It can come from plant or animal sources. A supplier declaration is needed to confirm the origin. Cystine is a sulfur-containing amino acid formed by the oxidation of two cysteine molecules. It is a major structural component of the hair protein keratin and is used in hair-care cosmetics. It can be derived from animal sources or produced synthetically.

Cystine

Unconfirmed

Cystine is a sulfur-containing amino acid formed by the oxidation of two cysteine molecules. It is a major structural component of the hair protein keratin and is used in hair-care cosmetics. It can be derived from animal sources or produced synthetically.

Also known as	3,3-Dithiobis(2-aminopropanoic acid), 3,3'-Dithiobis(2-aminopropanoic acid), Dicysteine, L-Cystine
CAS number	56-89-3
EC number	200-296-3
Last reviewed	16 April 2026

Classifications are made to the best of our knowledge based on available scientific and regulatory sources. We cannot guarantee the accuracy of every entry, errors in the sources we draw from can always occur. This tool also cannot account for cross-contamination, which depends entirely on individual suppliers and producers. If you believe a classification is incorrect, you can report an issue.

Is Cystine vegan?

Cystine

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