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Moumoujus

BENZOIC ACID.

Valuable CAS 65-85-0 / FRAGRANCE, pH ADJUSTERS, PRESERVATIVE

A multifunctional aromatic carboxylic acid primarily utilized for its robust antimicrobial properties and formula stabilization. Beyond its role as a preservative, it serves as a mild keratolytic agent and a penetration enhancer that facilitates the absorption of co-formulated active ingredients.

Summary

Preservative Tyrosinase Inhibitor Keratolytic Penetration Enhancer Fragrance Component

Science

Mechanism of Action

In its undissociated form, benzoic acid diffuses across microbial cell membranes to disrupt energy metabolism and cellular respiration. On the skin surface, it functions as a tyrosinase inhibitor to modulate melanin synthesis and acts as a mild desquamation agent by loosening the bonds between keratinocytes.

Research

Clinical Evidence

High confidence
Effective range 0.2–0.5%
Optimal

0.5%

Key findings

  1. 01 Morrow et al. (PMID 2339094) demonstrated that concentrations between 0.01-15% can induce dose-dependent biosynthesis of Prostaglandin D2, potentially causing cutaneous vasodilation.
  2. 02 SCCS Opinion SCCP/1016/06 confirmed that a 0.5% concentration provides effective antifungal and bacteriostatic activity within a pH range of 4.0 to 6.0.
  3. 03 Predictive modeling indicates that 0.2-0.5% represents the ideal equilibrium between antimicrobial efficacy and epidermal safety in leave-on emulsions.

Transparency

Dusting Analysis

Not commonly dusted
Min. effective
0.2%
Red flag below
0.1%

As a preservative and functional pH-adjuster, benzoic acid is rarely 'dusted' for marketing purposes. Usage below 0.2% generally fails to provide adequate antimicrobial protection unless synergistic boosters are present.

The Formula

Formulation

Solubility
Both
Optimal pH 3 – 5
0 7 14

Stability

Maximum efficacy is achieved below its pKa of 4.2; antimicrobial activity significantly diminishes as pH rises above 5.5. It is often paired with glycols like propanediol to enhance its solubility profile.

Synergies

  • Propanediol
  • Salicylic Acid
  • Glycols

Conflicts

  • Non-ionic surfactants (e.g., Polysorbate 80)
  • Strong oxidizing agents
  • Ferric salts
  • Cationic surfactants
  • Proteins

Safety

Safety Profile

CIR Status
Safe as used
Max tested
5%
Pregnancy
Safe
Sensitization risk Low

While the CIR allows up to 5.0%, the EU SCCS strictly limits leave-on products to 0.5% and rinse-off products to 2.5% to minimize the risk of erythema.

Your Skin

Skin Compatibility

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

Our Assessment

Verdict

Valuable

An essential precision preservative and performance booster that requires strict pH control (3.0-5.0) for optimal stability and skin compatibility.

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