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Moumoujus

TOLUENE SULFONIC ACID.

Questionable CAS 104-15-4 / SURFACTANT - CLEANSING, SURFACTANT - HYDROTROPE

Toluene Sulfonic Acid, also known as p-Toluenesulfonic acid or tosylic acid, is a powerful organic acid primarily utilized in skincare formulations for its exceptional ability to precisely adjust pH, often downwards. It also serves as a hydrotrope and surfactant, enhancing the solubility and cleansing efficacy of formulations when expertly incorporated.

Summary

pH regulator surfactant/cleansing hydrotrope

Science

Mechanism of Action

Functioning as a strong acid catalyst, Toluene Sulfonic Acid primarily works by protonating substrates, which can impact the pH of the skin's surface or the formulation itself. In a cosmetic context, its very low pKa (-2.8) signifies it will significantly lower a product's pH, serving as a potent pH regulator. It also exhibits properties as a hydrotrope, increasing the solubility of other compounds, and as a surfactant, contributing to cleansing actions.

Research

Clinical Evidence

Low confidence
Effective range N/A
Optimal

N/A

Transparency

Dusting Analysis

Not commonly dusted

The Formula

Formulation

Solubility
Water
Optimal pH N/A
0 7 14

Stability

This ingredient is a hygroscopic solid, highly soluble in water (67 g/100 mL at 25°C), alcohols, and ethers. Its exceptionally low pKa of -2.8 indicates it will profoundly decrease the pH of any formulation. While generally stable, it can exhibit instability under conditions of high temperature and pressure.

Conflicts

  • oxidizing agents (e.g., perchlorates, peroxides, permanganates, chlorates, nitrates, chlorine, bromine, fluorine)
  • metals
  • water (specifically for its anhydrous form, as it reacts strongly)
  • strong acids (e.g., hydrochloric, sulfuric, nitric)
  • ammonia
  • amines
  • isocyanates
  • vinyl acetate
  • epichlorohydrin

Safety

Safety Profile

CIR Status
Safe as used with restrictions
Sensitization risk Unknown

The Cosmetic Ingredient Review (CIR) Expert Panel deemed Toluene Sulfonic Acid safe for cosmetic use when precisely formulated to be nonirritating. It is a potent acid that is corrosive to skin at concentrations of 20% or above and can induce irritation at lower concentrations, posing a risk of severe skin burns and eye damage. p-Toluenesulfonates, potential byproducts, are recognized genotoxic impurities necessitating stringent monitoring in pharmaceutical applications at a threshold of 1.5 µg/day for extended treatments.

Your Skin

Skin Compatibility

Yes Normal
No Dry
Yes Oily
No Sensitive
Irritancy High
Comedogenicity Unknown

Our Assessment

Verdict

Questionable

While CIR-approved with strict restrictions, its high irritancy potential and corrosive nature necessitate extremely precise formulation to ensure non-irritating use, making its inclusion questionable for broad applications without specific, compelling benefits.

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