Science
Mechanism of Action
This molecule functions primarily as a direct or non-reactive hair dye, imparting color to the hair shaft. Its small molecular size allows for efficient diffusion into the hair, rather than interacting with skin directly for specific skincare benefits.
Research
Clinical Evidence
High confidence1%
Key findings
- 01 Regulatory assessments by the SCCS and SCCNFP establish a maximum on-head concentration of 1% for use in both oxidative and non-oxidative hair dye formulations. For permanent hair dyes, a pre-mixing concentration of 2% is permitted, which dilutes to 1% in-use.
Transparency
Dusting Analysis
As an ingredient specifically used for hair dyeing, Hydroxyethyl-2-nitro-p-toluidine is not typically utilized in precision skincare formulations for skin-specific benefits, therefore the concept of 'dusting' is not applicable.
The Formula
Formulation
Stability
A 0.03% aqueous solution exhibited acceptable stability (<3% variation) over seven days. However, a 0.18% aqueous solution at pH 6.4 demonstrated significant degradation, reducing to 36.1% over the same period. A 10% solution in DMSO showed stability with less than 7% variation over seven days, and manufacturers report stability under specific formulation conditions.
Conflicts
- As a secondary amine, this ingredient is susceptible to nitrosation, which can lead to the formation of undesirable nitrosamines.
- Potential incompatibilities exist with certain reactive ingredients, exemplified by its presence in formulations with dialkanolamines and other compounds like HC Blue 1, which carries a Carcinogenic 2B classification.
Safety
Safety Profile
The Scientific Committee on Consumer Safety (SCCS) has deemed Hydroxyethyl-2-nitro-p-toluidine safe for use in oxidative and non-oxidative hair dye formulations at a maximum on-head concentration of 1%. It is a regulated substance in Europe, listed under Annex III of the EC Cosmetics Regulation. While it is a secondary amine prone to nitrosation, the nitrosamine content in test materials was not reported in SCCS opinions. US FDA regulations offer exemptions for products containing this coal tar hair dye from specific adulteration provisions, provided the product label includes caution statements and patch test instructions.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Primarily functioning as a hair dye, this ingredient lacks known benefits for skin and presents safety considerations such as nitrosation potential, making it unsuitable for precision skincare formulations.
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References
Sources