Hair Dye
DIHYDROXYINDOLINE
Safety score · 0–100
Moderate
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
About
An indoline-type melanin precursor for progressive hair dye. Functional but reactive; SCCS concentration limits apply.
Dihydroxyindoline (CAS 29539-03-5) is the reduced (dihydro) form of dihydroxyindole, acting as a melanin precursor in progressive, non-oxidative hair-dye systems. It air-oxidizes in situ to form eumelanin-like pigments, giving natural-looking gradual coloring. SCCS has evaluated the hydroxyindole/indoline family in hair-dye dossiers and imposed concentration caps. Reactive indole-type chemistry gives positive signals in some in vitro genotoxicity assays; no CMR classification. Score in the Moderate/orange band — functional and regulated with limits, but reactive intermediate chemistry prevents a higher score.
Function
Skin benefits
- Progressive natural hair darkening
- No peroxide oxidation required
- Lower sensitization than PPD-class dyes
Known concerns
- Positive signal in some in vitro genotoxicity assays
- SCCS concentration limits
- Stains skin and surfaces
- Limited long-term data
References
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 — always read the physical product label and consult a healthcare professional for personal concerns.