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Moumoujus

4-AMINO-3-NITROPHENOL.

Avoid CAS 610-81-1 / HAIR DYEING

A specialized hair coloring agent that functions as both a direct dye and oxidative coupler to produce red and bordeaux tones. While effective in hair formulations with controlled dermal penetration rates, it presents significant sensitization concerns that limit its broader cosmetic applications.

Summary

hair dyeing color coupling pigment formation

Science

Mechanism of Action

Works through dual pathways: as a direct dye, its compact molecular structure penetrates hair cuticles without requiring oxidation, while in oxidative systems it couples with primary intermediates under peroxide conditions to form larger, permanent pigment complexes within the hair shaft.

Research

Clinical Evidence

High confidence
Effective range 1–1.5%
Optimal

1.5%

Key findings

  1. 01 Mini-pig dermal absorption study showing 5.62% penetration rate at 1.0% concentration in semi-permanent formulations
  2. 02 Reduced absorption to 2.83% when used at 1.5% in oxidative conditions with hydrogen peroxide
  3. 03 LLNA sensitization testing establishing EC3 threshold of 0.2%

Transparency

Dusting Analysis

Not commonly dusted

Primarily used in hair dye formulations at regulated concentrations rather than skincare products where dusting would be relevant.

The Formula

Formulation

Solubility
Both
Optimal pH 3 – 10
0 7 14

Stability

Demonstrates excellent stability in hair dye matrices but requires protection from light exposure and moisture due to hygroscopic properties. Maintains integrity for minimum 4 hours in appropriate solvents under inert conditions.

Synergies

  • p-phenylenediamines in oxidative systems
  • hydrogen peroxide for permanent color development

Conflicts

  • Strong oxidizing agents outside controlled reactions
  • Strong acids
  • UV light exposure

Safety

Safety Profile

CIR Status
Safe as used
Max tested
1.5%
Sensitization risk High

Classified as extreme sensitizer requiring mandatory patch testing and safety warnings. Regulatory approval limited to hair dye applications with strict concentration controls.

Your Skin

Skin Compatibility

Yes Normal
Yes Dry
Yes Oily
No Sensitive
Irritancy Low
Comedogenicity Unknown

Our Assessment

Verdict

Avoid

While technically effective for hair coloring, the extreme sensitization risk and regulatory restrictions make this ingredient unsuitable for precision skincare applications.

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