Sodium Isostearate
INCI: SODIUM ISOSTEARATE
Reviewed by Rosie · Last updated 14 Aug 2026
A synthetic fatty acid salt that cleanses and stabilises formulations
Best For Skin Types
All, Oily, Combination
Addresses
Usage Frequency
Daily
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What Is Sodium Isostearate?
Sodium isostearate is a synthetic surfactant derived from isostearic acid, a branched-chain fatty acid. It functions as a cleansing agent and emulsifier in skincare formulations, helping to lift oils and impurities from the skin whilst allowing water and oil-based ingredients to blend smoothly together.
This ingredient appears in a relatively small proportion of skincare products (around 0.1%), typically used in cleansers and emulsified formulations where stable, effective cleansing is the priority.
How It Works
As a surfactant, sodium isostearate has a molecular structure with both water-loving and oil-loving regions. This allows it to surround oil droplets and suspend them in water, making it possible to rinse away sebum and makeup. In formulations, it acts as a bridge between incompatible ingredients, creating stable, uniform textures.
Clinical Evidence & References
Research into isostearic acid and its derivatives suggests it has reasonable permeation-enhancing properties in topical formulations, making it a practical choice for delivery systems. However, direct clinical studies specifically evaluating sodium isostearate's safety or efficacy on human skin are limited in the published literature.
In animal studies examining comedogenic potential, isostearyl-derived ingredients have shown mixed results, though this data does not always translate directly to human skin. The ingredient is widely used in cosmetics at low concentrations and is generally considered safe for topical application.
How to Use
Sodium isostearate is typically a background ingredient in formulations rather than one to target specifically. Look for it in cleansers and emulsified moisturisers where a stable, effective formula is needed. As with all surfactants, use only as directed and rinse thoroughly if irritation occurs.
Safety & Precautions
Frequently Asked Questions
From the Clinic
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