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4-AMINO-2-HYDROXYTOLUENE SULFATE.

Avoid CAS 183293-62-1 / HAIR DYEING

4-amino-2-hydroxytoluene sulfate is a synthetic aromatic amine primarily engineered as a coupler in oxidative hair coloring systems. This water-soluble compound undergoes complex oxidation-coupling reactions to form permanent color molecules, but lacks established beneficial mechanisms for skincare applications.

hair dyeing color coupler

Science

Functions through oxidative coupling reactions where it combines with hydrogen peroxide developers and primary intermediates to create large pigment molecules. While theoretically possessing minor antioxidant properties typical of aromatic amines, it demonstrates no validated beneficial mechanisms for skin health or cosmetic enhancement.


Research

Medium confidence
Effective range 1.5–2.5%
Optimal

1.5%

Key findings

  1. 01 SCCS safety evaluation at 1.5% concentration in oxidative hair dye formulations confirmed consumer safety excluding sensitization concerns
  2. 02 CIR dermal irritation studies at 2.5% concentration demonstrated non-irritating properties to eyes and skin in rabbit models

Transparency

Not commonly dusted

Not applicable for skincare formulations as this ingredient is specifically designed for hair coloring applications and not intended for leave-on skin products


The Formula

Solubility
Water
Optimal pH 6.5 – 10
0 7 14

Stability

Demonstrates optimal stability in alkaline environments with pH 9-10. Exhibits photosensitivity and oxidative degradation requiring amber container storage. Sulfate salt form provides enhanced stability and water solubility compared to free base.

Synergies

  • Hydrogen peroxide developers
  • Para-phenylenediamine intermediates

Conflicts

  • Strong oxidizing agents outside intended color reactions
  • N-nitrosating agents due to nitrosamine formation risk
  • Strong acids

Safety

CIR Status
Safe as used
Max tested
1.5%
Pregnancy
Caution
Sensitization risk High

Regulatory approval limited to hair dye applications with 1.5% maximum concentration. Significant skin sensitization potential with documented cross-reactivity to para-phenylenediamine. Not recommended for leave-on skincare formulations.


Your Skin

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

Our Assessment

Avoid

Specialized hair coloring ingredient with high sensitization risk and no established skincare benefits, inappropriate for precision skincare formulations.


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