Ingredient review
Polyphenylsilsesquioxane/Trimethylsiloxysilicate
INCI: POLYPHENYLSILSESQUIOXANE/TRIMETHYLSILOXYSILICATE
A high-performance silicone resin that helps makeup and sunscreen stay put without feeling heavy.
In plain English
This is a type of silicone that forms a flexible, breathable film on your skin. It's often used in long-wear makeup and water-resistant sunscreens to help the product stay in place and resist sweat or water. Unlike some older silicones, it doesn't feel greasy or sticky and is generally well-tolerated even by sensitive 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
Polyphenylsilsesquioxane/Trimethylsiloxysilicate 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 Polyphenylsilsesquioxane/Trimethylsiloxysilicate.
- 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 silicone polymer composed of phenylsilsesquioxane and trimethylsiloxysilicate units, creating a crosslinked resin that dries to a smooth, flexible film.
How it works
When applied, the solvent evaporates and the silicone resin forms a thin, even film over the skin. This film locks in pigments and active ingredients, reduces transfer, and improves water resistance. It also helps other ingredients spread smoothly and evenly.
Pros
Excellent wear time
Forms a durable film that keeps makeup and sunscreen in place for hours, even in heat or humidity.
Lightweight feel
Unlike some heavy waxes or oils, this silicone resin dries to a smooth, non-tacky finish that doesn't clog pores.
Cons and cautions
Requires double cleansing
Because it's water-resistant, you'll likely need an oil-based cleanser or micellar water to remove it completely.
Environmental persistence
As a synthetic silicone, it does not readily biodegrade and may accumulate in the environment.
Best for
- People who want long-lasting makeup or sunscreen
- Those with oily or combination skin who prefer a matte finish
Use caution if
- Anyone who prefers easy, water-only makeup removal
Usage tips
Safety summary
Polyphenylsilsesquioxane/Trimethylsiloxysilicate is considered safe for cosmetic use. It has low irritation and comedogenic potential, making it suitable for most skin types. However, it may require thorough removal to avoid buildup.
Research notes
Safety assessments by the Cosmetic Ingredient Review (CIR) panel have concluded that this silicone resin is safe when used as intended. There is limited independent research on its long-term environmental impact.
Common label clues
- Typical concentration
- 1–10% in leave-on formulas
- Regulatory status
- Approved for use in cosmetics in the US, EU, and most major markets. The CIR panel has deemed it safe at typical use levels.
- Common uses
- Long-wear foundations, Waterproof mascara, Sunscreens, Lip products
- Environmental note
- Silicone resins like this are not biodegradable and can contribute to microplastic pollution. Some brands are moving toward more eco-friendly alternatives.
Good to know
- This ingredient is often listed near the end of INCI lists because it's used at low concentrations.
- It's considered safe by the Cosmetic Ingredient Review (CIR) panel for use in cosmetics.
Common questions
What is Polyphenylsilsesquioxane/Trimethylsiloxysilicate in beauty products?
This is a type of silicone that forms a flexible, breathable film on your skin. It's often used in long-wear makeup and water-resistant sunscreens to help the product stay in place and resist sweat or water. Unlike some older silicones, it doesn't feel greasy or sticky and is generally well-tolerated even by sensitive skin.
What does Polyphenylsilsesquioxane/Trimethylsiloxysilicate do in a beauty product?
When applied, the solvent evaporates and the silicone resin forms a thin, even film over the skin. This film locks in pigments and active ingredients, reduces transfer, and improves water resistance. It also helps other ingredients spread smoothly and evenly.
Is Polyphenylsilsesquioxane/Trimethylsiloxysilicate safe for most people?
Polyphenylsilsesquioxane/Trimethylsiloxysilicate is considered safe for cosmetic use. It has low irritation and comedogenic potential, making it suitable for most skin types. However, it may require thorough removal to avoid buildup.
Who should be careful with Polyphenylsilsesquioxane/Trimethylsiloxysilicate?
Anyone who prefers easy, water-only makeup removal
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.