Science
Mechanism of Action
In its established role, HC Blue No. 18 acts as a substantive dye, meaning it binds directly to the hair surface through physicochemical interactions to deposit color. This mechanism allows it to impart pigmentation without requiring oxidative reactions or significant penetration into the hair cortex, unlike some other hair colorants. It possesses no known therapeutic or functional mechanism for skin.
Research
Clinical Evidence
Low confidenceN/A
Transparency
Dusting Analysis
This ingredient's primary function is as a hair colorant; therefore, 'dusting' as it pertains to active skincare ingredients is not relevant.
The Formula
Formulation
Stability
The more polar anionic form of HC Blue No. 18 exhibits good solubility in water above a pH of 9.0. It has been determined to be stable in the presence of alkaline peroxide (e.g., MEA buffer at pH 10.0) for up to 45 minutes at 22°C, a characteristic crucial for its performance in hair dye applications. The phenolic form is soluble in organic solvents.
Safety
Safety Profile
The Scientific Committee on Consumer Safety (SCCS) has evaluated HC Blue No. 18, deeming it safe for use in non-oxidative and oxidative hair dye formulations at a maximum on-head concentration of 0.35%. However, it has been identified as a moderate sensitizer, indicating a potential for allergic reactions. No Cosmetic Ingredient Review (CIR) or FDA status for skincare use has been found.
Your Skin
Skin Compatibility
Our Assessment
Verdict
HC Blue No. 18 is primarily a hair dye with no demonstrated benefits for skin and carries a moderate sensitization risk, making its inclusion in precision skincare formulations highly questionable.
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