Science
Mechanism of Action
This ingredient operates by physically depositing colorant molecules onto the hair shaft, thereby imparting a yellow color. Its primary utility is in hair coloration, with no known mechanism of action or benefit for the skin.
Research
Clinical Evidence
Insufficient-data confidenceN/A
Transparency
Dusting Analysis
HC YELLOW NO. 9 is a colorant for hair applications and is not typically considered an active ingredient in skin care formulations requiring efficacy analysis through 'dusting'.
The Formula
Formulation
Stability
The ingredient has demonstrated stability in hair dye formulations when stored for a period of two months at room temperature.
Conflicts
- Nitrosating substances (due to potential for nitrosamine formation)
Safety
Safety Profile
As a secondary amine, HC YELLOW NO. 9 is susceptible to nitrosation, recommending avoidance with nitrosating substances and a nitrosamine content below 50 ppb. Purity concerns exist, with reported purities varying from 91.5% to 99% and impurities occasionally exceeding 8%. It is subject to use, concentration, or manufacturing restrictions within the EU Cosmetics Directive, with a maximum allowed concentration of 0.5% in semi-permanent hair dyes. The FDA lists it as a hair dyeing cosmetic ingredient.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Given its specific function as a hair dye, the absence of data regarding skin efficacy or compatibility, and existing safety concerns related to nitrosamine formation and material purity, HC YELLOW NO. 9 is not recommended for precision skincare formulations.
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References
Sources