Get a Free 5ml Mini Now Free 5ml Mini With Every Order of The Mantle
Moumoujus

ACID BLUE 9.

Optional CAS 3844-45-9 / HAIR DYEING

Acid Blue 9 (CI 42090) is a synthetic, water-soluble dye that imparts a vibrant greenish-blue hue to cosmetic formulations. It is utilized primarily for aesthetic enhancement in various personal care products.

Summary

colorant

Science

Mechanism of Action

This synthetic colorant achieves its brilliant hue by absorbing light within the 628-630 nm range. While in vitro studies suggest P2X7 receptor antagonism, this is not its intended mechanism of action in topical skincare.

Research

Clinical Evidence

Medium confidence
Effective range N/A
Optimal

0.5%

Transparency

Dusting Analysis

Not commonly dusted

The Formula

Formulation

Solubility
Water
Optimal pH 3 – 12
0 7 14

Stability

Highly stable within pH 3-12. Color may shift green below pH 3 or turn pink/decolorize above pH 12. Sensitive to oxidizing agents and certain metal ions.

Conflicts

  • Strong oxidizing agents
  • Strong reducing agents
  • Cationic surfactants
  • Copper and Iron ions

Safety

Safety Profile

CIR Status
Safe as used
Max tested
0.5%
Sensitization risk Low

FDA-approved for food (Blue 1), drugs, and externally applied cosmetics. The EU restricts its use to 0.5% in hair dye products and notes potential absorption through damaged skin or mucous membranes.

Your Skin

Skin Compatibility

Yes Normal
Yes Dry
Yes Oily
Yes Sensitive
Irritancy Low
Comedogenicity Low

Our Assessment

Verdict

Optional

Acid Blue 9 is a stable, water-soluble colorant widely approved for cosmetic use at concentrations up to 0.5%, offering aesthetic enhancement with low irritancy risk.

Related

Similar Ingredients

Finding similar ingredients…