Ingredient review
Hydrogenated Styrene/Methyl Styrene/Indene Copolymer
INCI: HYDROGENATED STYRENE/METHYL STYRENE/INDENE COPOLYMER
A synthetic film-former that helps makeup and skincare last longer and resist water, but offers no active skin benefits.
In plain English
This is a man-made plastic-like ingredient that creates a thin, flexible film on your skin or lashes. It helps makeup stay put longer, resist sweat and water, and gives a smooth finish. Think of it as a clear, invisible shield that holds your makeup in place. It doesn't moisturize or treat your skin—it's purely about performance and texture.
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
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Hydrogenated Styrene/Methyl Styrene/Indene 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 Hydrogenated Styrene/Methyl Styrene/Indene 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 synthetic polymer made from styrene, methyl styrene, and indene monomers that have been hydrogenated to make them more stable and less reactive. It is a solid resin that is dissolved in cosmetic oils or solvents to create a film when applied.
How it works
When applied, the solvent evaporates and the polymer chains link together to form a continuous, flexible film on the skin or hair. This film physically locks in pigments and other ingredients, improving water resistance, smudge resistance, and wear time. It also helps control the viscosity (thickness) of the product for easier application.
Pros
Excellent staying power
Creates a durable film that helps makeup resist fading, smudging, and transferring throughout the day.
Water and sweat resistant
Ideal for humid conditions, workouts, or tear-prone eyes—keeps products intact longer.
Cons and cautions
No skin benefit
This ingredient is purely functional—it doesn't hydrate, soothe, or treat the skin in any way.
Can be hard to remove
Because it forms a strong film, you'll likely need an oil-based cleanser or micellar water to fully remove it without rubbing.
Best for
- Anyone wanting long-wearing or waterproof makeup
- People with oily skin who need extra staying power
Use caution if
- Those who prefer minimal, lightweight formulas or who have very dry or sensitive skin that reacts to film-formers
Usage tips
Safety summary
Considered safe for cosmetic use at typical concentrations. Low irritation and comedogenic risk. No significant safety concerns reported in regulatory reviews.
Research notes
Limited independent studies on this specific polymer, but the broader class of hydrogenated styrene copolymers has been reviewed by the Cosmetic Ingredient Review (CIR) panel and found safe for use in cosmetics.
Common label clues
- Typical concentration
- 1–10% in most formulas
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions. No known restrictions at typical use levels.
- Common uses
- Long-wear foundations, Waterproof mascaras, Lip products, Sunscreens
- Environmental note
- As a synthetic polymer, it is not biodegradable and may contribute to microplastic pollution. Some brands are moving toward bio-based alternatives.
Good to know
- Hydrogenation makes the polymer more stable and less likely to yellow or degrade over time.
- Commonly found in 'transfer-proof' and '24-hour wear' makeup claims.
Common questions
What is Hydrogenated Styrene/Methyl Styrene/Indene Copolymer in beauty products?
This is a man-made plastic-like ingredient that creates a thin, flexible film on your skin or lashes. It helps makeup stay put longer, resist sweat and water, and gives a smooth finish. Think of it as a clear, invisible shield that holds your makeup in place. It doesn't moisturize or treat your skin—it's purely about performance and texture.
What does Hydrogenated Styrene/Methyl Styrene/Indene Copolymer do in a beauty product?
When applied, the solvent evaporates and the polymer chains link together to form a continuous, flexible film on the skin or hair. This film physically locks in pigments and other ingredients, improving water resistance, smudge resistance, and wear time. It also helps control the viscosity (thickness) of the product for easier application.
Is Hydrogenated Styrene/Methyl Styrene/Indene Copolymer safe for most people?
Considered safe for cosmetic use at typical concentrations. Low irritation and comedogenic risk. No significant safety concerns reported in regulatory reviews.
Who should be careful with Hydrogenated Styrene/Methyl Styrene/Indene Copolymer?
Those who prefer minimal, lightweight formulas or who have very dry or sensitive skin that reacts to film-formers
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.