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Ingredient directory

Quaternium-18 Methosulfate

Quaternium-18 Methosulfate is a positively charged quaternary ammonium compound, functioning as a versatile ingredient primarily valued for its conditioning, emulsifying, and surfactant properties in various cosmetic formulations.

Directory entry · Individual source review pending

This profile is awaiting an individual source review. Treat its ratings, dose estimates and compatibility labels as provisional; they are not medical advice or proof of a finished product’s effects.

Antistatic Conditioning Agent Emulsifier Hair Conditioning Suspending Agent Surfactant Viscosity Controlling Agent

Science

Mechanism of Action

As a quaternary ammonium compound, Quaternium-18 Methosulfate possesses a positive charge, allowing it to electrostatically bind to the negatively charged surfaces inherent in skin and hair. This interaction enables its diverse functions, including conditioning, acting as a surfactant, emulsifying immiscible phases, suspending particulates, and regulating product viscosity. Its emulsifying capacity specifically stabilizes oil-in-water formulations, preventing component separation.

Research

Clinical Evidence

Low confidence
Effective range N/A
Optimal

N/A

Transparency

Dusting Analysis

Not commonly dusted

The Formula

Formulation

Solubility
Unknown
Optimal pH 4 – 6
0 7 14

Stability

The compound demonstrates optimal pH stability within the range of 4.0 to 6.0. As an emulsifier, it actively stabilizes oil-in-water formulations, which is critical for preventing component separation and maintaining product integrity.

Safety

Safety Profile

CIR Status
Safe as used
Sensitization risk Unknown

The Cosmetic Ingredient Review (CIR) Expert Panel has concluded that related compounds, Quaternium-18, Quaternium-18 Bentonite, and Quaternium-18 Hectorite, are safe for use in cosmetics. This finding was reaffirmed in 2003 and 2019, with the latter clarification noting no inhalation toxicity concerns for Quaternium-18 due to its large particle size. However, specific maximum concentration data for Quaternium-18 Methosulfate itself were not explicitly provided in the available CIR tables.

Your Skin

Skin Compatibility

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

Our Assessment

Verdict

Optional

Quaternium-18 Methosulfate is a CIR-deemed safe, multi-functional ingredient providing formulation stability and conditioning benefits, although specific skin efficacy and compatibility data for this exact compound are currently limited.

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