Ingredient review
Hydroxystearic Acid
INCI: Hydroxystearic Acid
A gentle, plant-derived fatty acid that helps stabilize formulas and gives a smooth, non-greasy feel.
In plain English
Hydroxystearic acid is a fatty acid made from castor oil. In skincare, it helps thicken creams and lotions, keeps oil and water mixed together, and gives products a silky, spreadable texture. It's considered very gentle and unlikely to clog pores or irritate 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.
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
Hydroxystearic Acid 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 Hydroxystearic Acid.
- 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
A modified fatty acid derived from castor oil, chemically altered to improve its thickening and stabilizing properties in cosmetic formulations.
How it works
It acts as a thickening agent and emulsifier, helping to create a stable, smooth mixture of oil and water. It also helps control the viscosity (thickness) of a product, making it easier to apply and giving it a pleasant, non-greasy feel on the skin.
Pros
Gentle on skin
Hydroxystearic acid has a very low irritation and comedogenic risk, making it suitable for sensitive and acne-prone skin types.
Improves product feel
It gives creams and lotions a smooth, silky texture that spreads easily without leaving a heavy or greasy residue.
Cons and cautions
Not a skin-active ingredient
Its primary role is to improve formula texture and stability, not to deliver direct skin benefits like hydration or anti-aging.
Rare allergy potential
Since it is derived from castor oil, individuals with a rare castor allergy may experience a reaction, though this is extremely uncommon.
Best for
- Anyone looking for a gentle, non-irritating thickener in their moisturizers or makeup
- People with oily or combination skin who prefer a non-greasy finish
Use caution if
- Individuals with a known allergy to castor oil or its derivatives (very rare)
Usage tips
Safety summary
Hydroxystearic acid is considered safe for use in cosmetics at typical concentrations. It has a low potential for irritation and is not known to be comedogenic. Allergic reactions are extremely rare.
Research notes
The safety of hydroxystearic acid has been reviewed by the Cosmetic Ingredient Review (CIR) panel, which concluded it is safe for use in cosmetic products. Most available data focus on its function as a thickener and emulsifier rather than direct skin benefits.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and other major markets. The Cosmetic Ingredient Review (CIR) panel has deemed it safe as used in cosmetics.
- Common uses
- Creams, Lotions, Lipsticks, Foundations, Hair conditioners
- Environmental note
- Derived from castor oil, a renewable plant source. The manufacturing process is generally considered low-impact, but specific sourcing and processing can vary.
Good to know
- Hydroxystearic acid is often used in lipsticks and foundations to help them glide on smoothly.
- It is considered a 'clean' ingredient by many green beauty standards due to its plant origin and mildness.
Common questions
What is Hydroxystearic Acid in beauty products?
Hydroxystearic acid is a fatty acid made from castor oil. In skincare, it helps thicken creams and lotions, keeps oil and water mixed together, and gives products a silky, spreadable texture. It's considered very gentle and unlikely to clog pores or irritate skin.
What does Hydroxystearic Acid do in a beauty product?
It acts as a thickening agent and emulsifier, helping to create a stable, smooth mixture of oil and water. It also helps control the viscosity (thickness) of a product, making it easier to apply and giving it a pleasant, non-greasy feel on the skin.
Is Hydroxystearic Acid safe for most people?
Hydroxystearic acid is considered safe for use in cosmetics at typical concentrations. It has a low potential for irritation and is not known to be comedogenic. Allergic reactions are extremely rare.
Who should be careful with Hydroxystearic Acid?
Individuals with a known allergy to castor oil or its derivatives (very rare)
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.