Hair Dye Intermediate
4-Hydroxyindole, when used as a substance in hair dye products
Safety score · 0–100
Moderate
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
About
4-Hydroxyindole — a hair-dye coupler restricted under EU Annex III with a maximum permitted concentration. Skin-sensitization potential means formulation control and on-product warnings are essential.
Skin benefits
- Hair dye coupler
- Indole-class colour development
Known concerns
- EU Annex III restricted in hair dyes
- Skin sensitization potential
- Eye and skin irritation
- Not allowed in cosmetics outside coupler use
- Limited toxicological dataset
References
EU CosIng database
European Commission cosmetic ingredient registry — regulatory status, restrictions, authorised functions.
Related hair dye intermediates
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This profile is for educational purposes and does not constitute medical advice. Regulatory status and scientific understanding evolve — always read the physical product label and consult a healthcare professional for personal concerns.