Ingredient review
Polybutylene Terephthalate
INCI: POLYBUTYLENE TEREPHTHALATE
A synthetic plastic-like polymer that helps makeup last longer and resist smudging, but offers no skincare benefit.
In plain English
Polybutylene Terephthalate is a type of plastic polymer used in cosmetics to create a flexible, durable film on the skin or lashes. Think of it like a clear, invisible layer that helps makeup stay put without cracking or flaking. It's most often found in long-wear mascaras, eyeliners, and lip products to improve water resistance and wear time.
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
Polybutylene Terephthalate 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 Polybutylene Terephthalate.
- 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 thermoplastic polyester resin, related to the polyester family, engineered to form a thin, flexible film when applied to skin or hair.
How it works
When the product dries, the polymer molecules link together into a continuous film that adheres to the surface. This film locks in pigments and other ingredients, creating a water-resistant, smudge-proof barrier that extends wear time.
Pros
Excellent wear time
Creates a durable film that keeps makeup intact for hours, even in humid conditions.
Smooth application
Helps formulas glide on evenly and dry down to a non-tacky finish.
Cons and cautions
Synthetic origin
Derived from petroleum, which may be a concern for eco-conscious users.
Potential stiffness
In high concentrations, the film can feel stiff or heavy on delicate skin, especially around the eyes.
Best for
- Anyone seeking long-wearing, smudge-proof eye or lip makeup
- People with normal to oily skin who want makeup to stay in place
Use caution if
- Those with very sensitive eyes or contact lens discomfort
- Individuals who prefer entirely natural or biodegradable cosmetics
Usage tips
Safety summary
Polybutylene Terephthalate is considered safe for topical use in cosmetics at typical concentrations. It has a low irritation and comedogenic risk, but like all film-formers, it may cause discomfort if it enters the eyes or if used on compromised skin.
Research notes
Limited independent safety studies specific to cosmetic use, but it is structurally similar to other polyester film-formers that have a long history of safe use. The Cosmetic Ingredient Review (CIR) has not published a specific monograph on PBT, but related polyesters are generally recognized as safe.
Common label clues
- Typical concentration
- Typically 1–10% in formulas
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions. No known restrictions at typical concentrations.
- Common uses
- Mascara, Eyeliners, Lipsticks, Long-wear foundations
- Environmental note
- As a synthetic plastic, it is not biodegradable and may contribute to microplastic pollution if rinsed into waterways.
Good to know
- Often combined with other film-formers like acrylates copolymer for enhanced flexibility.
- Commonly listed near the top of ingredient lists in waterproof mascaras.
Common questions
What is Polybutylene Terephthalate in beauty products?
Polybutylene Terephthalate is a type of plastic polymer used in cosmetics to create a flexible, durable film on the skin or lashes. Think of it like a clear, invisible layer that helps makeup stay put without cracking or flaking. It's most often found in long-wear mascaras, eyeliners, and lip products to improve water resistance and wear time.
What does Polybutylene Terephthalate do in a beauty product?
When the product dries, the polymer molecules link together into a continuous film that adheres to the surface. This film locks in pigments and other ingredients, creating a water-resistant, smudge-proof barrier that extends wear time.
Is Polybutylene Terephthalate safe for most people?
Polybutylene Terephthalate is considered safe for topical use in cosmetics at typical concentrations. It has a low irritation and comedogenic risk, but like all film-formers, it may cause discomfort if it enters the eyes or if used on compromised skin.
Who should be careful with Polybutylene Terephthalate?
Those with very sensitive eyes or contact lens discomfort Individuals who prefer entirely natural or biodegradable cosmetics
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.