Ingredient review
Butadiene/Isoprene Copolymer
INCI: BUTADIENE/ISOPRENE COPOLYMER
A synthetic rubber that helps makeup last longer and resist water, but offers no skin benefit.
In plain English
Butadiene/Isoprene Copolymer is a synthetic rubber ingredient used in cosmetics to create a flexible, water-resistant film on the skin or lashes. It helps makeup stay put longer, especially in mascaras and long-wear lipsticks. Think of it as a clear, invisible plastic wrap that locks in your makeup but doesn't do anything active for your 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
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Butadiene/Isoprene 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 Butadiene/Isoprene 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 butadiene and isoprene monomers, chemically similar to the rubber used in tires. In cosmetics, it's processed into a fine powder or liquid dispersion that dries into a flexible film.
How it works
When applied, the copolymer forms a thin, elastic film on the skin or hair surface. This film acts as a barrier that resists water, sweat, and smudging, while also helping other ingredients adhere better. It also thickens the product's texture, making it easier to apply evenly.
Pros
Excellent film former
Creates a durable, flexible film that helps makeup resist water, sweat, and rubbing, so your look lasts longer without flaking.
Improves product texture
Adds a smooth, creamy feel to formulas, making application easier and more even, especially in mascaras and eyeliners.
Cons and cautions
No skin benefit
This ingredient is purely functional—it doesn't hydrate, soothe, or protect the skin. It's there only to improve product performance.
Potential for heavy feel
In high concentrations, it can leave a tacky or stiff residue on the skin or lashes, which some users find uncomfortable.
Best for
- Anyone wanting long-lasting, waterproof makeup
- People with oily eyelids who need mascara or liner that won't smudge
Use caution if
- Those who prefer minimal, natural ingredient lists or avoid synthetic polymers
Usage tips
Safety summary
Butadiene/Isoprene Copolymer is considered safe for cosmetic use at typical concentrations. It has low irritation and comedogenic potential. However, it is a synthetic material with no skin benefit and may not align with clean beauty preferences.
Research notes
Safety assessments by the Cosmetic Ingredient Review (CIR) panel have concluded that similar synthetic polymers are safe when formulated properly. No significant human or animal studies specifically on this copolymer were found, but its chemical class is well-tolerated.
Common label clues
- Typical concentration
- Typically 1–10% in rinse-off or leave-on formulas
- Regulatory status
- Approved for use in cosmetics in the US (FDA), EU (CosIng), and many other regions. No known restrictions at typical use levels.
- Common uses
- Mascara, Eyeliners, Long-wear lip products, Water-resistant sunscreens
- Environmental note
- As a synthetic polymer derived from fossil fuels, it is not biodegradable. Its environmental impact is similar to other plastic-based ingredients used in cosmetics.
Good to know
- Butadiene/Isoprene Copolymer is considered safe for use in cosmetics by major regulatory bodies, but it is not biodegradable and is derived from petroleum.
- It is often used in combination with other film formers to balance flexibility and durability.
Common questions
What is Butadiene/Isoprene Copolymer in beauty products?
Butadiene/Isoprene Copolymer is a synthetic rubber ingredient used in cosmetics to create a flexible, water-resistant film on the skin or lashes. It helps makeup stay put longer, especially in mascaras and long-wear lipsticks. Think of it as a clear, invisible plastic wrap that locks in your makeup but doesn't do anything active for your skin.
What does Butadiene/Isoprene Copolymer do in a beauty product?
When applied, the copolymer forms a thin, elastic film on the skin or hair surface. This film acts as a barrier that resists water, sweat, and smudging, while also helping other ingredients adhere better. It also thickens the product's texture, making it easier to apply evenly.
Is Butadiene/Isoprene Copolymer safe for most people?
Butadiene/Isoprene Copolymer is considered safe for cosmetic use at typical concentrations. It has low irritation and comedogenic potential. However, it is a synthetic material with no skin benefit and may not align with clean beauty preferences.
Who should be careful with Butadiene/Isoprene Copolymer?
Those who prefer minimal, natural ingredient lists or avoid synthetic polymers
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.