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Moumoujus

BENZALPHTHALIDE.

Valuable CAS 575-61-1 / UV ABSORBER

A specialized aromatic lactone utilized primarily for its ability to shield complex cosmetic formulations from light-induced degradation. By neutralizing ultraviolet radiation, it ensures that photosensitive active ingredients maintain their structural integrity and therapeutic efficacy over time.

Summary

UV Absorber Light Stabilizer Photostability Enhancer

Science

Mechanism of Action

Benzalphthalide functions as a dedicated UV quencher and light stabilizer. Its molecular structure contains a conjugated aromatic system that absorbs UV energy and converts it into kinetic thermal energy, preventing the photolysis of sensitive compounds and protecting the skin from secondary oxidative stress caused by UV exposure.

Research

Clinical Evidence

Medium confidence
Effective range 0.1–5%
Optimal

2%

Key findings

  1. 01 Evaluation of light stabilization in topical minocycline delivery systems (US Patent 9539266).
  2. 02 Assessment of 3-benzalphthalide derivatives for secondary antimicrobial and photoprotective properties.

Transparency

Dusting Analysis

Not commonly dusted
Min. effective
0.1%
Red flag below
0.05%

Benzalphthalide is rarely used as a 'hero' ingredient for marketing; it is typically included at functional levels (0.1%+) to provide genuine stability to the formulation rather than for label-claim 'dusting'.

The Formula

Formulation

Solubility
Oil
Optimal pH 4 – 7
0 7 14

Stability

Maintain pH below 8.0 to prevent alkaline hydrolysis, which can cause the lactone ring to open and diminish its stabilizing properties.

Synergies

  • Photosensitive vitamins (Retinol, Vitamin C)
  • Unstable pharmaceutical actives
  • Organic UV filters

Conflicts

  • Strong oxidizing agents
  • High pH environments (>8.0)
  • Strong mineral acids

Safety

Safety Profile

CIR Status
Not reviewed
Max tested
5%
Sensitization risk Moderate

Recognized in the EU CosIng database. Potential for mild skin and eye irritation in higher concentrations; patch testing is recommended for reactive skin types.

Your Skin

Skin Compatibility

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

Our Assessment

Verdict

Valuable

An essential stabilizer for high-performance, precision formulas containing light-sensitive actives that requires careful pH management.

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References

Sources