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METHYLIMIDAZOLIUMPROPYL P-PHENYLENEDIAMINE HCL.

Avoid CAS 220158-86-1 / HAIR DYEING

METHYLIMIDAZOLIUMPROPYL P-PHENYLENEDIAMINE HCL is a highly water-soluble derivative of p-phenylenediamine, specifically engineered as an oxidative hair coloring agent. Despite its approved use in hair dye formulations up to 2% concentration on-head, it carries a significant risk as a potent skin sensitizer.

Summary

hair dye

Science

Mechanism of Action

As an oxidative hair dye component, this p-phenylenediamine derivative functions by reacting with oxidizing agents to produce color. On the skin, it is understood to induce allergic contact dermatitis, similar to its related compound p-Phenylenediamine (PPD), through a mechanism potentially involving the upregulation of thymic stromal lymphopoietin (TSLP) and inflammatory cytokines.

Research

Clinical Evidence

Insufficient-data confidence
Effective range N/A
Optimal

N/A

Transparency

Dusting Analysis

Not commonly dusted

The Formula

Formulation

Solubility
Water
Optimal pH N/A
0 7 14

Stability

Highly water-soluble (>1 kg/L in pure water at 20°C ± 5°C) with no observed pH-dependency for solubility. As a p-phenylenediamine derivative, it is designed to react with oxidizing agents such as hydrogen peroxide. The compound is susceptible to degradation from strong light, heat, and oxygen, which can lead to oxidation and polymerization; therefore, careful stability considerations with developers are crucial.

Conflicts

  • oxidizing agents (e.g., hydrogen peroxide)
  • strong light
  • heat
  • oxygen

Safety

Safety Profile

CIR Status
Not reviewed
Max tested
2%
Sensitization risk High

The Scientific Committee on Consumer Safety (SCCS) deems METHYLIMIDAZOLIUMPROPYL P-PHENYLENEDIAMINE HCL safe for oxidative hair coloring applications at an on-head concentration not exceeding 2%. However, the SCCS explicitly classifies it as a strong skin sensitizer. The Cosmetic Ingredient Review (CIR) Expert Panel has assessed related p-Phenylenediamine compounds as safe for hair dye use but unsafe for direct dermal coloring applications or in eyelash/eyebrow dyes, highlighting a consistent concern with skin contact for this class of ingredients. FDA mandates specific warnings for coal-tar hair dyes, which include p-phenylenediamine derivatives.

Your Skin

Skin Compatibility

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

Our Assessment

Verdict

Avoid

This ingredient is a potent oxidative hair dye and a confirmed strong skin sensitizer; it is definitively not recommended for topical skincare formulations due to its high risk of eliciting allergic contact dermatitis.

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References

Sources