Science
Mechanism of Action
Functions as a direct dye coating in semi-permanent formulations or undergoes oxidative coupling in permanent hair dyes to form larger imine complexes that become trapped within hair structure. On skin contact, it metabolizes into triaminobenzene and N4-acetyl-2NPPD compounds.
Research
Clinical Evidence
High confidence1.1%
Key findings
- 01 Non-irritating at 2.5% concentration in rabbit primary skin irritation study (PII = 0)
- 02 Sensitization observed in 20% of guinea pigs at 3.0% concentration
- 03 Human patch test confirmed positive sensitization reaction at 2.0% in occupational exposure case
Transparency
Dusting Analysis
Concentrations above 1.1% significantly increase sensitization risk, with documented allergic reactions at 2.0% and above in both animal and human studies
The Formula
Formulation
Stability
Solid form demonstrates good storage stability but readily oxidizes in aqueous solution forming reactive intermediates. Solution exhibits pH-dependent color changes appearing reddish orange.
Conflicts
- Nitrosating agents
- Ferric chloride
- Oxidizing agents
Safety
Safety Profile
CIR Panel concluded safety only for non-sensitized individuals. Banned in EU under Annex II due to toxicity concerns. US permits use in hair products with mandatory caution statements and patch testing requirements.
Your Skin
Skin Compatibility
Our Assessment
Verdict
While effective for hair coloring, the high sensitization risk and regulatory restrictions make this ingredient problematic for widespread cosmetic use.
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References
Sources