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Moumoujus

USNIC ACID.

Insufficient Data CAS 125-46-2 / ANTIMICROBIAL

A lichen-derived compound, Usnic Acid offers broad-spectrum antimicrobial, anti-inflammatory, and antioxidant benefits. It is particularly effective for acne-prone skin and shows promise in photoprotection and wound healing.

Summary

Science

Mechanism of Action

It inhibits P. acnes and other microbes, modulates inflammatory pathways to reduce redness, and neutralizes free radicals. Usnic acid also promotes skin regeneration through enhanced fibroblast activity and collagen deposition, alongside UV-absorbing properties.

Research

Clinical Evidence

High confidence
Effective range 0.0001–2%
Optimal

N/A

Key findings

  1. 01 Demonstrates inhibition of Propionibacterium acnes (P. acnes) at concentrations as low as ≥ 0.0001%.
  2. 02 (+)-Usnic acid at 1% in cosmetic formulations exhibits photoprotective properties comparable to octocrylene, with enhanced efficacy when combined.
  3. 03 Commercial anti-acne products successfully utilize 1% usnic acid for targeted treatment. For sensitive skin, leave-on products are recommended between 0.1% and 0.5%.

Transparency

Dusting Analysis

Not commonly dusted

The Formula

Formulation

Solubility
Oil
Optimal pH 5 – 6.5
0 7 14

Stability

Optimal stability is achieved within a pH range of 5.0-6.5. Its lipophilic nature and low water solubility necessitate solid dispersion techniques for optimal integration into formulations.

Synergies

  • Octocrylene (enhanced photoprotection and stability)

Conflicts

  • strong acids
  • strong bases

Safety

Safety Profile

CIR Status
Not reviewed
Max tested
2%
Sensitization risk Low

The FDA considers usnic acid GRAS for topical use, with SCCS offering formulation guidance. Topical application is safer than oral, and contact sensitivity is rare, particularly for the preferred (+)-enantiomer and concentrations below 0

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