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HC YELLOW NO. 4.

Optional CAS 59820-43-8 / HAIR DYEING

HC Yellow No. 4 is a synthetic organic compound utilized primarily as a non-oxidative hair dye, imparting color through diffusion into the hair fiber or surface adhesion. Research indicates minimal dermal absorption upon topical application.

Summary

Hair dyeing Colorant

Science

Mechanism of Action

This compound functions exclusively as a hair colorant, lacking any described direct mechanism of action or beneficial effect on skin physiology. Its low molecular weight allows for penetration into the hair shaft in semi-permanent applications, while for temporary dyes, it adheres to the hair surface. Any interaction with the skin is typically limited to potential temporary staining.

Research

Clinical Evidence

Low confidence
Effective range N/A
Optimal

N/A

Key findings

  1. 01 Little dermal absorption observed.
  2. 02 No sensitization reactions.

Transparency

Dusting Analysis

Not commonly dusted

HC Yellow No. 4 is a cosmetic colorant and not an active ingredient intended for direct skincare benefits. Consequently, the concept of 'dusting,' which relates to optimal concentrations for therapeutic skin efficacy, is not applicable to this compound.

The Formula

Formulation

Solubility
Water
Optimal pH ≤9
0 7 14

Stability

Optimal stability in hair coloring products is achieved at approximately pH 9; formulations exceeding this pH may lead to decomposition. This compound is susceptible to degradation from prolonged exposure to light and heat, necessitating storage in protected conditions. While specific hair dye formulation stability is not extensively detailed, DMSO solutions were stable for 7 days at -20 ± 10°C, and no change was observed after a 30-minute reaction with hydrogen peroxide in a 1% hair color formulation.

Conflicts

  • Nitrosating substances (due to potential for nitrosamine formation)

Safety

Safety Profile

CIR Status
Safe as used
Max tested
1.5%
Sensitization risk Low

The Cosmetic Ingredient Review (CIR) Expert Panel deemed HC Yellow No. 4 safe as a hair colorant under current usage practices. The Scientific Committee on Consumer Safety (SCCS) similarly considered it safe for use as a non-oxidative hair dye at a maximum concentration of 1.5%. As a secondary amine, it carries a potential for nitrosation; therefore, it must not be combined with nitrosating substances, and the nitrosamine content in the final product should be below 50 ppb. The FDA provides regulatory oversight for colorants in cosmetic products.

Your Skin

Skin Compatibility

Yes Normal
Yes Dry
Yes Oily
Yes Sensitive
Irritancy Unknown
Comedogenicity Unknown

Our Assessment

Verdict

Optional

HC Yellow No. 4 is a well-researched hair colorant with a low risk of dermal absorption or sensitization, making it an optional ingredient for cosmetic coloration, though it provides no direct skincare benefits.

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