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BASIC YELLOW 40.

Optional CAS 29556-33-0 / HAIR DYEING

A cationic fluorescent dye primarily utilized for its vibrant aesthetic properties and electrostatic binding capabilities. In precision formulations, it is valued for its ability to adhere to protein structures and exhibit intense yellow-green fluorescence under specific light wavelengths.

colorant hair dyeing fluorescent marker

Science

This ingredient functions as a cationic (positively charged) compound that establishes electrostatic bonds with negatively charged substrates, such as hair keratin. It exhibits high-intensity fluorescence when excited by light in the 365–485 nm spectral range, making it highly effective for targeted color deposition and forensic identification.


Research

Medium confidence
Effective range 0.0001–1%
Optimal

1%

Key findings

  1. 01 In vitro research by Ho Y S et al. (2005) demonstrated that at concentrations of 10^-4 M, the molecule can interact with phospholipid membranes to inhibit fatty acid and cholesterol synthesis.
  2. 02 SCCS/1509/13 safety assessments confirmed that at a 1.0% concentration, the ingredient exhibits minimal dermal absorption and negligible systemic bioavailability.

Transparency

Not commonly dusted
Min. effective
0.1%
Red flag below
0.01%

As a colorant and hair-dyeing agent, concentrations below 0.1% are generally insufficient for visual performance and may indicate label-only inclusion.


The Formula

Solubility
Both
Optimal pH 2 – 5
0 7 14

Stability

Maintains peak stability within acidic environments (pH 2.0-5.0). Stability significantly decreases in alkaline conditions. Highly soluble in both aqueous solutions and alcohols like ethanol.

Synergies

  • Cationic surfactants
  • Alcohol-based delivery systems

Conflicts

  • Anionic surfactants
  • Strong oxidizing agents
  • Strong reducing agents
  • Nitrosating systems

Safety

CIR Status
Safe with restrictions
Max tested
1%
Sensitization risk Low

Must meet strict purity standards: free from primary aromatic amines (aniline) and containing less than 50 µg/kg of nitrosamines.


Your Skin

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

Our Assessment

Optional

A highly effective cationic colorant for hair and specialized fluorescent applications with a strong safety profile and minimal skin penetration.


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