Ingredient review
Lactic Acid/Hydroxystearic Acid Copolymer
INCI: Lactic Acid/Hydroxystearic Acid Copolymer
A gentle film-forming polymer that helps makeup and sunscreen last longer without feeling heavy or sticky.
In plain English
This ingredient is a polymer, which is a long chain of repeating molecules. It's made from lactic acid (a natural alpha hydroxy acid) and hydroxystearic acid (a fatty acid). When applied to skin, it dries down to form a thin, flexible, invisible film. This film helps other ingredients stay put, improves water resistance, and gives a smooth, even feel. It's commonly used in sunscreens and long-wear makeup to prevent them from sliding off or fading.
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
Lactic Acid/Hydroxystearic Acid Copolymer 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 Lactic Acid/Hydroxystearic Acid Copolymer.
- 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 semi-synthetic copolymer created by chemically linking lactic acid and hydroxystearic acid. It functions primarily as a film former and texture enhancer in cosmetic formulations.
How it works
After application, the copolymer forms a continuous, breathable film on the skin's surface. This film acts as a barrier that reduces the migration of other ingredients (like sunscreen filters or pigments), helping them stay in place longer. It also imparts a silky, non-tacky feel and can improve the water resistance of products.
Pros
Boosts product longevity
Creates a flexible film that helps sunscreen and makeup resist sweat, water, and rubbing, so you don't have to reapply as often.
Lightweight feel
Unlike some heavy waxes or silicones, this copolymer dries to a thin, silky layer that doesn't feel sticky or greasy on the skin.
Cons and cautions
Potential tightness on dry skin
The film-forming effect can sometimes feel slightly tightening or drying for those with very dry or compromised skin barriers.
Limited independent safety data
While generally considered safe, there are fewer long-term studies on this specific copolymer compared to more common film-formers.
Best for
- Anyone wanting longer-lasting makeup or sunscreen
- People with oily or combination skin who prefer a matte finish
Use caution if
- Those with extremely dry or dehydrated skin who may find film-formers uncomfortable
Usage tips
Safety summary
Lactic Acid/Hydroxystearic Acid Copolymer is considered safe for topical use at typical cosmetic concentrations. It has low irritation and comedogenic potential. No significant safety concerns have been reported in regulatory reviews.
Research notes
Research on this specific copolymer is limited, but it is structurally similar to other well-studied film-forming polymers used in cosmetics. Safety assessments rely on its low reactivity and history of safe use in commercial products.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and other major markets. No known restrictions at typical use levels.
- Common uses
- Sunscreens, Foundations, Long-wear makeup, Moisturizers
- Environmental note
- As a synthetic polymer, it may not be biodegradable. However, its low use concentration and rinse-off behavior vary by product type.
Good to know
- This ingredient is often listed near the end of an ingredient list because it's used at low concentrations.
- It is not a sunscreen active ingredient but helps sunscreens stay effective longer by improving water resistance.
Common questions
What is Lactic Acid/Hydroxystearic Acid Copolymer in beauty products?
This ingredient is a polymer, which is a long chain of repeating molecules. It's made from lactic acid (a natural alpha hydroxy acid) and hydroxystearic acid (a fatty acid). When applied to skin, it dries down to form a thin, flexible, invisible film. This film helps other ingredients stay put, improves water resistance, and gives a smooth, even feel. It's commonly used in sunscreens and long-wear makeup to prevent them from sliding off or fading.
What does Lactic Acid/Hydroxystearic Acid Copolymer do in a beauty product?
After application, the copolymer forms a continuous, breathable film on the skin's surface. This film acts as a barrier that reduces the migration of other ingredients (like sunscreen filters or pigments), helping them stay in place longer. It also imparts a silky, non-tacky feel and can improve the water resistance of products.
Is Lactic Acid/Hydroxystearic Acid Copolymer safe for most people?
Lactic Acid/Hydroxystearic Acid Copolymer is considered safe for topical use at typical cosmetic concentrations. It has low irritation and comedogenic potential. No significant safety concerns have been reported in regulatory reviews.
Who should be careful with Lactic Acid/Hydroxystearic Acid Copolymer?
Those with extremely dry or dehydrated skin who may find film-formers uncomfortable
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.