Oxidative hair dye precursor
4,5-Diamino-1-(2- hydroxyethyl)-1H- pyrazole
Safety score · 0–100
Fine
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
A pyrazole-based oxidative hair dye precursor that reacts with peroxide and couplers to develop permanent hair colour. CIR considers the sulfate salt safe up to 3% in oxidative hair dyes, with sensitisation as the main risk.
Skin benefits
- Oxidative hair dye precursor that contributes to permanent hair colour shades
- Allows formulation of paraphenylenediamine-free dye systems
Known concerns
- CIR concluded the sulfate salt is safe up to 3% on-head, but with documented sensitisation potential
- Oxidative hair dye precursors can trigger allergic contact dermatitis in sensitised users
- Requires use with peroxide oxidiser and other coupler ingredients
- Stricter EU and US labelling requirements apply to oxidative hair dyes
References
EU CosIng database
European Commission cosmetic ingredient registry: regulatory status, restrictions, authorised functions.
Related oxidative hair dye precursors
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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.