4-HYDROXYINDOLE
Safety score · 0–100
Caution
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
About
A heterocyclic phenolic compound restricted in EU cosmetic formulations under Annex II reference II/1220 as a hair dye substance.
4-Hydroxyindole is listed in EU Regulation 1223/2009 Annex II under reference II/1220, indicating it is prohibited for use as a substance in cosmetic products. The Annex II list contains substances prohibited in cosmetic products across all EU member states. 4-Hydroxyindole was historically used as an intermediate or precursor in oxidative hair dyeing systems, but regulatory assessment identified risks that led to its prohibition in cosmetic formulations within the EU market.
Known concerns
- EU Annex II prohibited substance (reference II/1220)
- Banned from all cosmetic product types in EU
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.