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2,6-DIMETHOXY-3,5-PYRIDINEDIAMINE HCL.

Avoid CAS 56216-28-5 / HAIR DYEING

A pyridine-based chemical compound specifically engineered as an oxidative precursor for permanent hair coloring systems. This ingredient functions as a developer/coupler that creates stable color molecules when activated by hydrogen peroxide, exclusively used in professional and at-home hair dye formulations rather than traditional skincare applications.

Hair dyeing precursor Oxidative color developer

Science

Functions through oxidative coupling chemistry where hydrogen peroxide triggers the formation of large, stable pigment molecules that permanently deposit within the hair shaft structure


Research

High confidence
Effective range 0.25–0.25%
Optimal

0.25%

Key findings

  1. 01 SCCP safety assessment at 3.0% showed no skin irritation in repeated guinea pig applications
  2. 02 AICIS assessment confirmed 5.4 µg/cm² dermal absorption at 0.25% concentration with hydrogen peroxide

Transparency

Not commonly dusted

Not applicable to skincare formulations as this ingredient is exclusively used in hair coloring systems


The Formula

Solubility
Water
Optimal pH 3 – 3
0 7 14

Stability

Exhibits limited aqueous stability with 10% degradation within 48 hours at pH 3; demonstrates improved stability in cream base formulations lasting up to 8 weeks at 20°C

Synergies

  • Hydrogen peroxide for oxidative activation

Conflicts

  • Strong oxidizing agents outside controlled reactions
  • Alkaline pH environments above 3.0

Safety

CIR Status
Not reviewed
Max tested
0.25%
Sensitization risk High

SCCS approved for hair dye applications at maximum 0.25% concentration; classified as GHS Category 1A sensitizer with significant acute oral toxicity concerns


Your Skin

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

Our Assessment

Avoid

Specialized hair dye ingredient with no skincare benefits and significant sensitization risks inappropriate for facial or body care formulations.


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