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Moumoujus

M-AMINOPHENOL HCL.

Avoid CAS 51-81-0 / HAIR DYEING

M-Aminophenol HCl functions as a key secondary intermediate within permanent oxidative hair dye formulations. Its role is to react with precursors and hydrogen peroxide, forming large, colored molecules that become entrapped within the hair shaft, providing durable hair coloration. This ingredient is not associated with direct skincare benefits.

Summary

Hair dye Oxidative colorant

Science

Mechanism of Action

M-Aminophenol HCl operates specifically within the oxidative hair dyeing process. It acts as a coupler, engaging in chemical reactions with colorless developer precursors and hydrogen peroxide to synthesize larger, intensely colored molecules. These color compounds are designed to be too voluminous to exit the hair shaft, resulting in a permanent color change. There is no identified mechanism of action for direct benefits on the skin.

Research

Clinical Evidence

Insufficient-data confidence
Effective range N/A
Optimal

N/A

Transparency

Dusting Analysis

Commonly dusted

M-Aminophenol HCl is exclusively an oxidative hair dye component, with no identified skin benefits or efficacy data. Its inclusion in a precision skincare formulation would therefore be without functional purpose for the skin.

The Formula

Formulation

Solubility
Water
Optimal pH N/A
0 7 14

Stability

Solutions of m-Aminophenol (1.0 mg/ml) in 0.5% methyl cellulose remain stable for up to 6 hours at room temperature when stored under an inert atmosphere and protected from light. When refrigerated at 4°C, stability extends to approximately 9 days. The final color intensity and shade achieved in hair dyeing formulations are sensitive to the pH conditions.

Conflicts

  • Hydrogen peroxide (as it is a reactant in its primary function)
  • Strong oxidizing agents (due to its involvement in oxidative reactions)
  • Light and air (which compromise its stability in solution)
  • Other aromatic p-amino compounds and azo dyes (due to potential for cross-allergies)

Safety

Safety Profile

CIR Status
Safe as used
Max tested
1.2%
Sensitization risk High

The Cosmetic Ingredient Review (CIR) Expert Panel deemed m-Aminophenol safe for its intended use as a hair dye. The SCCS (Scientific Committee on Consumer Products) similarly concluded its safety as an oxidative hair dye at a maximum on-head concentration of 1.2% in the final product after mixing, despite its known sensitizing potential. Consequently, cosmetic products containing this substance are legally required to display a label warning about the risk of sensitization. While a 2% concentration was non-irritating to rabbit skin, studies using a Local Lymph Node Assay (LLNA) in mice showed sensitizing potential at concentrations of 0.5% and above.

Your Skin

Skin Compatibility

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

Our Assessment

Verdict

Avoid

M-Aminophenol HCl is a hair dye ingredient with a demonstrated risk of sensitization and no known benefits for skin, rendering it unsuitable for precision skincare formulations.

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