Science
Mechanism of Action
As an oxidative hair colorant, P-Methylaminophenol reacts with an oxidant, such as hydrogen peroxide, to form an imine. This imine then combines with a coupler within the hair fiber, ultimately producing an indophenol dye that imparts color.
Research
Clinical Evidence
Low confidenceN/A
Key findings
- 01 SCCNFP (1999) considered it safe for permanent hair dye formulations at an in-use concentration of 1.5% (from 3.0% pre-mix), provided a sensitization warning label is present.
- 02 SCCS (2006) observed its use in oxidative hair dye at 0.68% in-use (from 1.35% pre-mix), estimating dermal absorption up to 6.19 ± 2.24 µg/cm² under non-oxidative conditions.
- 03 SCCP (2006) and a 2015 assessment identified it as a moderate skin sensitizer with an effective concentration (EC3) of 2.2%, and expected to cause only slight skin irritation at concentrations up to 3%.
Transparency
Dusting Analysis
This ingredient is a functional hair dye, not a skincare active. Its usage is strictly regulated by safety thresholds rather than efficacy requirements for skin benefits. Therefore, the concept of 'dusting' for enhanced performance in skincare is not applicable.
The Formula
Formulation
Stability
Aqueous solutions exhibit acidic behavior (pH < 7.0). Solutions are sensitive to light and require storage protected from sunlight and heat, preferably under an inert atmosphere, for stability lasting several days (e.g., 0.5 mg/ml stable up to 4 days, 200 mg/ml up to 9 days at room temperature or 4°C).
Conflicts
- Bases (due to its acidic nature in solution)
- Nitrosating agents (as a secondary amine, it is prone to nitrosation)
Safety
Safety Profile
The CIR Expert Panel deemed it safe for hair dye use under restrictions. The EU Cosmetics Directive permits a maximum in-use concentration of 1.5% (derived from 3.0% pre-mix) for hair dyeing. It is classified as hazardous ('May cause sensitisation by skin contact' - R43) and is a known human skin toxicant or allergen with strong evidence. As a secondary amine, it is susceptible to nitrosation. FDA regulates its use as a colorant in cosmetics.
Your Skin
Skin Compatibility
Our Assessment
Verdict
P-Methylaminophenol is a hair dye ingredient with no reported benefits for skin and presents a significant risk of moderate skin sensitization, classifying it as unsuitable for Moumoujus skincare formulations.
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