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N-PHENYL-P-PHENYLENEDIAMINE SULFATE.

Avoid CAS 4698-29-7 / HAIR DYEING

N-Phenyl-p-Phenylenediamine Sulfate is a synthetic organic compound primarily employed as a precursor in permanent (oxidative) hair dyeing formulations. It enables the creation of lasting color by forming polymeric molecules within the hair fiber.

Summary

Hair Dyeing

Science

Mechanism of Action

As a primary intermediate in oxidative hair dye systems, N-Phenyl-p-Phenylenediamine Sulfate undergoes a chemical reaction with a coupling agent and an oxidizing agent (such as hydrogen peroxide). This reaction forms large, colored polymeric molecules that are deposited inside the hair shaft, resulting in a durable and long-lasting color change. This mechanism is specific to hair dyeing and does not confer beneficial effects on the skin.

Research

Clinical Evidence

Insufficient-data confidence
Effective range N/A
Optimal

N/A

Transparency

Dusting Analysis

Not commonly dusted

This ingredient serves a specific purpose in hair dyeing and is not typically associated with 'dusting' or overuse in general cosmetic applications for perceived benefits.

The Formula

Formulation

Solubility
Water
Optimal pH N/A
0 7 14

Stability

The compound appears as needles or crystals when in solution and generally maintains stability under normal conditions. Its color formation efficiency in oxidative hair dyes is sensitive to the pH of the dyeing solution.

Conflicts

  • air contact
  • direct sunlight
  • moisture
  • oxidizers (should be mixed immediately before use in hair dyes)
  • dermal coloring applications (e.g., temporary black henna tattoos)
  • eyelash and eyebrow dyes

Safety

Safety Profile

CIR Status
Safe with restrictions
Max tested
1.7%
Sensitization risk High

The CIR Expert Panel has deemed N-Phenyl-p-Phenylenediamine Sulfate safe for use in hair dyes at concentrations up to 1.7% (as the free base). However, it is explicitly considered unsafe for direct dermal coloring applications, such as temporary black henna tattoos, and for use in products applied to eyelashes and eyebrows. The European Union Cosmetics Regulation permits a maximum concentration of 6.0% (calculated as free base) for hair dyeing. The FDA restricts p-Phenylenediamine and its derivatives as unapproved color additives for any cosmetic product other than hair dye, specifically prohibiting its use in eye makeup or temporary tattoos.

Your Skin

Skin Compatibility

No Normal
No Dry
No Oily
No Sensitive
Irritancy High
Comedogenicity Unknown

Our Assessment

Verdict

Avoid

N-Phenyl-p-Phenylenediamine Sulfate is an ingredient specifically designed for permanent hair coloring and carries a high irritancy risk. It is strictly not recommended for any skincare applications due to regulatory prohibitions and safety concerns regarding dermal exposure.

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