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Colorant

Sodium 4-[(2-hydroxy-1-naphthyl)azo]benzene sulfonate

CAS 633-96-5
50

Safety score · 0–100

Moderate

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

An azo benzenesulfonate red colorant — used mostly in rinse-off hair-dye formulations under EU restrictions. Like other azo dyes, it can carry aromatic-amine impurity and sensitization risks.

Function

HAIR DYEING

Skin benefits

  • Vibrant colorant for hair products
  • Stable in rinse-off

Known concerns

  • Azo dye — aromatic-amine impurity risk
  • Possible sensitization
  • EU restrictions on hair-dye use

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.