Ingredient review
Sodium Hydroxystearate
INCI: Sodium Hydroxystearate
A mild cleansing ingredient that helps create a rich lather and stable bar soaps, generally well-tolerated by most skin types.
In plain English
Sodium Hydroxystearate is a soap-like ingredient made from castor oil. It helps cleansers foam up and removes dirt and oil from your skin. Because it's derived from a natural oil and processed to be gentle, it's less drying than many traditional soaps.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- semi synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Sodium Hydroxystearate is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Sodium Hydroxystearate.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
Sodium Hydroxystearate is the sodium salt of 12-hydroxystearic acid, a fatty acid derived from castor oil. It acts as a surfactant, meaning it helps water mix with oil and dirt so they can be rinsed away.
How it works
In a cosmetic product, Sodium Hydroxystearate reduces the surface tension of water, allowing it to penetrate oils and lift grime from the skin. It also helps stabilize the lather and texture of bar soaps and cleansers.
Pros
Gentle on skin
Compared to traditional sodium tallowate or sodium cocoate soaps, Sodium Hydroxystearate is less alkaline and less likely to cause tightness or irritation after washing.
Good lather in bars
It helps bar soaps produce a stable, creamy foam that feels luxurious and spreads easily, improving the user experience.
Cons and cautions
Can be drying at high levels
In very high concentrations or in formulations without added moisturizers, it may still leave dry or sensitive skin feeling tight or stripped.
Limited to rinse-off use
This ingredient is not designed for leave-on products like lotions or serums, so its benefits are confined to cleansing steps.
Best for
- People with normal to oily skin looking for a mild cleanser
- Anyone who prefers bar soaps over liquid cleansers
Use caution if
- Individuals with extremely dry or compromised skin barriers who may benefit from non-foaming cleansers
Usage tips
Safety summary
Sodium Hydroxystearate is considered safe for use in rinse-off cosmetics at typical concentrations. It has low irritation and comedogenic potential, making it suitable for most skin types. As with any cleansing ingredient, overuse or high concentrations may cause dryness in sensitive individuals.
Research notes
Safety assessments by the Cosmetic Ingredient Review (CIR) panel have concluded that hydroxystearic acid and its salts are safe in cosmetic formulations when formulated to be non-irritating. Studies indicate low acute toxicity and minimal skin sensitization potential.
Common label clues
- Typical concentration
- 1-10% in rinse-off products
- Regulatory status
- Approved for use in cosmetics in the US (FDA) and EU (CosIng) with no concentration restrictions for rinse-off products.
- Common uses
- Bar soaps, Facial cleansers, Shaving creams
- Environmental note
- Derived from castor oil, a renewable plant source, and generally considered biodegradable, though its production involves chemical processing.
Good to know
- Sodium Hydroxystearate is often used in transparent or translucent soap bars to improve clarity.
- It is considered biodegradable and more environmentally friendly than some petroleum-based surfactants.
Common questions
What is Sodium Hydroxystearate in beauty products?
Sodium Hydroxystearate is a soap-like ingredient made from castor oil. It helps cleansers foam up and removes dirt and oil from your skin. Because it's derived from a natural oil and processed to be gentle, it's less drying than many traditional soaps.
What does Sodium Hydroxystearate do in a beauty product?
In a cosmetic product, Sodium Hydroxystearate reduces the surface tension of water, allowing it to penetrate oils and lift grime from the skin. It also helps stabilize the lather and texture of bar soaps and cleansers.
Is Sodium Hydroxystearate safe for most people?
Sodium Hydroxystearate is considered safe for use in rinse-off cosmetics at typical concentrations. It has low irritation and comedogenic potential, making it suitable for most skin types. As with any cleansing ingredient, overuse or high concentrations may cause dryness in sensitive individuals.
Who should be careful with Sodium Hydroxystearate?
Individuals with extremely dry or compromised skin barriers who may benefit from non-foaming cleansers
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.