Is Cysteine vegan?

Cysteine

Unconfirmed

L-Cysteine is a naturally occurring sulfur-containing amino acid that oxidises to form the disulfide cystine. It is used in cosmetics as a hair-conditioning agent and in food processing. It can be sourced from animal keratin (hair, feathers) or produced synthetically/by fermentation.

Also known as 2-Amino-3-mercaptopropionic acid, Half-cystine, L-Cysteine, L-Cysteine hydrochloride
E number E920
CAS number 52-90-4
EC number 200-158-2
Last reviewed 16 April 2026

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