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BASIC ORANGE 31.

Optional CAS 97404-02-9 / HAIR DYEING

A synthetic cationic direct dye primarily utilized for its high-affinity coloring properties in hair and scalp formulations. It serves a purely aesthetic function, providing vibrant orange hues through surface-level deposition rather than metabolic skin intervention.

colorant hair dye

Science

This molecule operates through electrostatic attraction; its positive charge (cationic) binds to the negatively charged keratin proteins found in the stratum corneum and hair shaft. It functions as a surface colorant, adhering to the outermost layers with minimal percutaneous penetration into deeper dermal tissues.


Research

High confidence
Effective range 0.5–1%
Optimal

1%

Key findings

  1. 01 SCCS/1334/10: Assessment of 1.0% concentration in non-oxidative dyes showing low absorption (0.2%) and safe topical profile.
  2. 02 SCCS/1358/10: Evaluation of 0.5% concentration in oxidative environments confirming no significant systemic toxicity.

Transparency

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

As a potent synthetic dye, 'dusting' is rarely an issue because even minute amounts produce significant visual pigment. However, concentrations below 0.1% in a product marketed for 'color refreshing' may be insufficient for noticeable results.


The Formula

Solubility
Water
Optimal pH 3.5 – 9
0 7 14

Stability

Maintains peak stability between pH 4.0 and 7.0; prolonged exposure to environments exceeding pH 9.0 can lead to chemical degradation and loss of chromatic intensity.

Synergies

  • Cationic conditioners
  • Hydrogen peroxide (in oxidative systems)

Conflicts

  • Anionic surfactants
  • Strong reducing agents
  • Strong oxidizing agents (outside of specific oxidative dye kits)

Safety

CIR Status
Safe as used
Max tested
1%
Sensitization risk Moderate

Recognized as a potential skin sensitizer. In the EU, products containing this ingredient must alert consumers to the risk of allergic reactions.


Your Skin

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

Our Assessment

Optional

A safe and effective surface colorant for hair and specialized scalp applications, though it offers no biological skin benefits and requires caution for sensitive users.


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References