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INCI: CYSTEINE
A sulfur-containing amino acid that acts as an antioxidant and is a building block for proteins like keratin, often used in hair and nail products for strengthening.
Beneficial for
May aggravate
Safety summary
Generally recognized as safe.
CAS Number
52-90-4
For informational purposes only. This is not medical advice. Always patch test new products and consult a dermatologist for skin concerns.