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BASIC YELLOW 11.

Avoid CAS 4208-80-4 / HAIR DYEING

A cationic methine dye primarily utilized for its intense pigmenting properties in temporary hair and textile applications. While it possesses secondary antioxidant and photostabilizing capabilities, its high irritancy profile makes it a rare and controversial inclusion in leave-on skincare.

colorant photostabilizer antioxidant

Science

As a cationic molecule, it binds to negatively charged keratinous surfaces to provide color. Biochemically, it functions as a UV absorber and a quencher of singlet oxygen and superoxide anions, protecting photosensitive active ingredients from oxidative degradation during sun exposure.


Research

Low confidence
Effective range 2–10%
Optimal

5%

Key findings

  1. 01 Research indicates that at concentrations between 2-10%, this molecule effectively absorbs UV radiation (290–400 nm) and stabilizes other cosmetic actives by neutralizing reactive oxygen species.

Transparency

Not commonly dusted
Min. effective
2%
Red flag below
0.1%

In skincare, this ingredient is rarely used for its primary function. If present at very low levels (below 0.1%), it is likely used as a cosmetic colorant rather than for its patented photostabilizing benefits, which require much higher concentrations.


The Formula

Solubility
Water
Optimal pH 3 – 7
0 7 14

Stability

Highly soluble in ethanol and hot water; maintains stability in acidic to neutral environments. It undergoes decomposition into colorless forms or precipitates if the pH exceeds 8.5.

Synergies

  • Photosensitive active ingredients
  • UV filters

Conflicts

  • Anionic surfactants (SLS/SLES)
  • Strong oxidizing agents
  • Copper ions
  • Iron ions
  • Strongly alkaline bases

Safety

CIR Status
Not reviewed
Max tested
10%
Pregnancy
Caution
Sensitization risk High

Prohibited for use in hair dyes within the European Union (Annex II). It is not FDA-certified for general cosmetic use and shows evidence of moderate toxicity and significant skin sensitization potential.


Your Skin

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

Our Assessment

Avoid

Despite its interesting photostabilizing properties, its high irritancy rating and regulatory prohibitions in major markets make it unsuitable for precision skincare.


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