ACID RED 51 — Moumoujus

ACID RED 51.

Avoid CAS 16423-68-0; 1342-25-2 / COLORANT, HAIR DYEING

Acid Red 51, also known as Erythrosine, is a xanthene dye primarily used as a cosmetic colorant, imparting a cherry-pink to red hue. While effective as a biological stain for non-viable cells and plaque, it offers no active skincare benefits.

colorant

Science

Mechanism of Action

This tetraiodofluorescein dye functions by absorbing and reflecting light in the visible spectrum (λmax ~525-530nm) to create color. It also binds to proteins and cellular structures, which facilitates its use as a biological stain.

Research

Clinical Evidence

Low confidence

Effective range 0.1–1%

Optimal

N/A

Transparency

Dusting Analysis

Not commonly dusted

The Formula

Formulation

Solubility

Water

Optimal pH 6 – 7

0 7 14

Stability

Highly stable in neutral to alkaline conditions (pH 6-7), but sensitive to photolysis in aqueous solutions and can precipitate in acidic environments.

Conflicts

strong oxidizing agents
strong acids
some metallic ions

Safety

Safety Profile

CIR Status

Not reviewed

Max tested

Sensitization risk Low

The FDA terminated Acid Red 51's provisional listing for cosmetics and externally applied drugs in 1990 due to concerns over thyroid tumors in high-dose animal studies. It remains restricted, though permitted in hair dyes up to 1% in the EU.

Your Skin

Skin Compatibility

Yes Normal

Yes Dry

Yes Oily

No Sensitive

Irritancy Low

Comedogenicity Low

Our Assessment

Verdict

Avoid

Due to its non-functional role in skincare and past FDA termination for cosmetic use, this ingredient is not recommended for topical formulations.

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