Ingredient review
PEI-45/TMP/Xylene Diisocyanate Crosspolymer
INCI: PEI-45/TMP/XYLENE DIISOCYANATE CROSSPOLYMER
A synthetic film-former that helps makeup and sunscreen stay put longer, generally considered safe at low concentrations.
In plain English
This is a man-made polymer that creates a thin, flexible film on your skin. Think of it like a clear, invisible shield that helps makeup resist sweat, water, and rubbing. It's commonly used in long-wear and waterproof products to keep them from smudging or fading throughout the day.
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
PEI-45/TMP/Xylene Diisocyanate Crosspolymer 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 PEI-45/TMP/Xylene Diisocyanate Crosspolymer.
- 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 crosslinked polymer made from polyethyleneimine (PEI), trimethylolpropane (TMP), and xylene diisocyanate. It forms a durable, flexible film when applied to the skin.
How it works
When the product dries, the polymer molecules link together to form a continuous, water-resistant film on the skin's surface. This film physically locks in pigments and other ingredients, preventing them from transferring or washing off easily.
Pros
Boosts wear time
Helps makeup and sunscreen resist sweat, water, and friction, so you don't need to reapply as often.
Improves sunscreen efficacy
By forming a uniform film, it can help sunscreen actives stay evenly distributed on the skin, potentially boosting SPF performance.
Cons and cautions
Synthetic origin
Made from petrochemicals, which may be a concern if you prefer naturally derived ingredients.
Can be drying
The film can feel tight or drying on very dry or sensitive skin, especially in high concentrations.
Best for
- Anyone wanting long-wearing makeup or sunscreen
- People with oily or combination skin who need extra staying power
Use caution if
- Those who prefer exclusively natural or plant-based ingredients
- Individuals with known sensitivity to synthetic polymers (rare)
Usage tips
Safety summary
Generally considered safe for topical use in cosmetics at typical concentrations. No significant irritation or sensitization has been reported in standard tests. As with any ingredient, patch test if you have very sensitive skin.
Research notes
Limited independent studies on this specific polymer, but the broader class of polyurethane-based film formers has been reviewed by the CIR and found safe. Most evidence comes from manufacturer safety data and regulatory approvals.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and many other regions. The Cosmetic Ingredient Review (CIR) panel has evaluated similar crosspolymers and found them safe at typical use levels.
- Common uses
- Long-wear foundations, Waterproof mascaras, Sunscreens, Lip products
- Environmental note
- As a synthetic polymer, it is not biodegradable. However, it is used in very small amounts and is not known to accumulate in the environment at concerning levels.
Good to know
- This ingredient is often listed near the end of ingredient lists because it's used in small amounts.
- It is not absorbed into the skin; it stays on the surface as a film.
- The 'PEI' part refers to polyethyleneimine, a polymer that helps the film adhere to skin.
Common questions
What is PEI-45/TMP/Xylene Diisocyanate Crosspolymer in beauty products?
This is a man-made polymer that creates a thin, flexible film on your skin. Think of it like a clear, invisible shield that helps makeup resist sweat, water, and rubbing. It's commonly used in long-wear and waterproof products to keep them from smudging or fading throughout the day.
What does PEI-45/TMP/Xylene Diisocyanate Crosspolymer do in a beauty product?
When the product dries, the polymer molecules link together to form a continuous, water-resistant film on the skin's surface. This film physically locks in pigments and other ingredients, preventing them from transferring or washing off easily.
Is PEI-45/TMP/Xylene Diisocyanate Crosspolymer safe for most people?
Generally considered safe for topical use in cosmetics at typical concentrations. No significant irritation or sensitization has been reported in standard tests. As with any ingredient, patch test if you have very sensitive skin.
Who should be careful with PEI-45/TMP/Xylene Diisocyanate Crosspolymer?
Those who prefer exclusively natural or plant-based ingredients Individuals with known sensitivity to synthetic polymers (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.