Ingredient review
Potassium Hydroxystearate
INCI: POTASSIUM HYDROXYSTEARATE
An effective cleanser and emulsifier, but may be drying or irritating for sensitive skin in high concentrations.
In plain English
Potassium Hydroxystearate is a soap-like ingredient made from castor oil. It helps water and oil mix together so that cleansers can remove dirt and makeup, and creams can feel smooth. Because it's a soap, it can be quite strong and may strip natural oils from the skin, especially if you have dry or sensitive skin.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Main practical flags: irritation is moderate; clogging risk is low.
- Source
- semi synthetic
- Evidence
- moderate
- Irritation
- moderate
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Potassium Hydroxystearate can be useful, but watch for some irritation potential.
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 Potassium 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
moderateCan bother some users, especially with frequent use, damaged skin, or strong companion ingredients.
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
A potassium salt of hydroxystearic acid, produced by reacting castor oil with potassium hydroxide. It acts as a surfactant (cleansing agent) and an emulsifier (helps blend oil and water).
How it works
In a cleanser, it surrounds oil and dirt particles so they can be rinsed away with water. In a cream or lotion, it helps keep the oil and water phases mixed together so the product stays smooth and doesn't separate.
Pros
Strong cleanser
Effectively removes excess oil, sunscreen, and makeup without needing harsh scrubbing.
Good emulsifier
Helps create stable, creamy textures in lotions and creams, improving product feel and performance.
Cons and cautions
Can be drying
Its soap-like nature can strip the skin's natural moisture barrier, leading to tightness or flakiness, especially in dry climates.
Potential irritation
May cause stinging or redness on sensitive or compromised skin, particularly in high concentrations or leave-on products.
Best for
- People with oily or combination skin looking for a thorough cleanse
- Those who prefer bar soaps or traditional cream cleansers
Use caution if
- Individuals with dry, dehydrated, or eczema-prone skin
- Anyone with known sensitivity to soap-based cleansers
Usage tips
Safety summary
Generally safe for use in rinse-off cosmetics at typical concentrations. May cause dryness or irritation in sensitive individuals or when used in high amounts. Not recommended for leave-on products on compromised skin.
Research notes
Limited direct studies on Potassium Hydroxystearate itself. Its safety is inferred from related fatty acid salts and from its long history of use in soap-making. The Cosmetic Ingredient Review (CIR) has evaluated similar fatty acid salts and found them safe when formulated to be non-irritating.
Common label clues
- Typical concentration
- 1–10% in rinse-off products; lower in leave-on formulas
- Regulatory status
- Approved for use in cosmetics in the EU, US, and other major markets. No specific concentration restrictions, but formulators are advised to keep levels low in leave-on products to minimize irritation.
- Common uses
- Facial cleansers, Bar soaps, Creams and lotions
- Environmental note
- Derived from castor oil, a renewable plant source. It is biodegradable and generally considered low in aquatic toxicity.
Good to know
- Potassium Hydroxystearate is often found in transparent or translucent bar soaps.
- It is biodegradable and derived from renewable castor oil, making it a more sustainable choice than some petroleum-based surfactants.
Common questions
What is Potassium Hydroxystearate in beauty products?
Potassium Hydroxystearate is a soap-like ingredient made from castor oil. It helps water and oil mix together so that cleansers can remove dirt and makeup, and creams can feel smooth. Because it's a soap, it can be quite strong and may strip natural oils from the skin, especially if you have dry or sensitive skin.
What does Potassium Hydroxystearate do in a beauty product?
In a cleanser, it surrounds oil and dirt particles so they can be rinsed away with water. In a cream or lotion, it helps keep the oil and water phases mixed together so the product stays smooth and doesn't separate.
Is Potassium Hydroxystearate safe for most people?
Generally safe for use in rinse-off cosmetics at typical concentrations. May cause dryness or irritation in sensitive individuals or when used in high amounts. Not recommended for leave-on products on compromised skin.
Who should be careful with Potassium Hydroxystearate?
Individuals with dry, dehydrated, or eczema-prone skin Anyone with known sensitivity to soap-based 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.