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Hair smoothing / aldehyde donor

GLYOXYLOYL CYSTEINE

45

Safety score · 0–100

Moderate

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

A cysteine-based hair smoothing active that reforms internal hair bonds under heat. Though promoted as formaldehyde-free, it can release small amounts of formaldehyde during high-heat ironing.

Function

HAIR WAVING OR STRAIGHTENING

Skin benefits

  • Smooths and temporarily straightens hair via cysteine cross-link reformation
  • Marketed as a gentler alternative to formaldehyde treatments
  • Improves manageability and reduces frizz

Known concerns

  • Releases formaldehyde when heated with flat irons at high temperatures
  • Respiratory irritation risk for stylists and clients
  • Scalp irritation and contact dermatitis reported
  • Inhalation hazard during application

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.