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Skin Conditioning

CYSTEINE

CAS 52-90-4 / 3374-22-9
85

Safety score · 0–100

Good

Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.

A natural sulfur amino acid that helps build skin and hair proteins. Considered very safe at cosmetic levels with extensive food and pharmaceutical use history.

Skin benefits

  • Sulfur-containing amino acid
  • Antioxidant via thiol group
  • Supports keratin and skin proteins

Known concerns

  • Possible sulfur odor at higher levels
  • Oxidizes readily; formula stability matters

References

EU

EU CosIng database

European Commission cosmetic ingredient registry: regulatory status, restrictions, authorised functions.

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This profile is for educational purposes and does not constitute medical advice. Regulatory status and scientific understanding evolve, so always read the physical product label and consult a healthcare professional for personal concerns.