Ingredient review
Polymethylsilsesquioxane/Trimethylsiloxysilicate
INCI: POLYMETHYLSILSESQUIOXANE/TRIMETHYLSILOXYSILICATE
A silicone film former that gives makeup a smooth, long-lasting finish without feeling heavy or greasy.
In plain English
This ingredient is a type of silicone that forms a thin, flexible film on your skin. It helps makeup and skincare products spread evenly, feel silky, and stay put longer. Because it's not absorbed into the skin, it sits on the surface and can help reduce water loss without clogging pores for most people.
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
Polymethylsilsesquioxane/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 Polymethylsilsesquioxane/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 blend that combines two silicone types to create a durable, water-resistant film on the skin or hair.
How it works
When applied, it forms a uniform, breathable film that smooths the skin's surface, reduces the appearance of fine lines and pores, and helps other ingredients stay in place. It also provides a slight water-resistant barrier.
Pros
Long-lasting finish
Helps makeup and sunscreen resist smudging, fading, and transferring throughout the day.
Smooth texture
Creates a velvety, non-greasy feel that blurs pores and fine lines for a more even complexion.
Cons and cautions
Removal challenge
Because it forms a water-resistant film, you'll need an oil-based cleanser or micellar water to fully remove it without residue.
Potential tightness
On very dry or dehydrated skin, the film can feel slightly tightening or uncomfortable, especially if layered with other film formers.
Best for
- People with oily or combination skin who want a matte, long-lasting finish
- Anyone looking for a primer or foundation that stays put through humidity or long days
Use caution if
- Those who prefer silicone-free or minimalist routines
- Individuals with very dry skin who may find film formers too tightening
Usage tips
Safety summary
Polymethylsilsesquioxane/Trimethylsiloxysilicate is considered safe for cosmetic use at typical concentrations. It has low irritation and comedogenic potential, though individuals with very sensitive or dry skin may experience mild tightness. No serious safety concerns have been reported in regulatory reviews.
Research notes
Safety assessments by the Cosmetic Ingredient Review (CIR) panel have concluded that similar silicone film formers are safe as used in cosmetics. Peer-reviewed studies confirm low skin irritation and sensitization potential. Evidence for long-term environmental impact is still emerging.
Common label clues
- Typical concentration
- 1% to 10% in leave-on products
- Regulatory status
- Approved for use in cosmetics globally, including by the FDA (USA) and EU CosIng database, with no known restrictions at typical use levels.
- Common uses
- Foundations, Primers, Sunscreens, Long-wear makeup, Eye shadows
- Environmental note
- As a silicone, it may not be biodegradable. Some manufacturers are exploring more eco-friendly alternatives, but it remains widely used for its performance.
Good to know
- This ingredient is often combined with other silicones to adjust feel and durability.
- It is considered non-comedogenic for most skin types, but patch test if you are prone to breakouts.
Common questions
What is Polymethylsilsesquioxane/Trimethylsiloxysilicate in beauty products?
This ingredient is a type of silicone that forms a thin, flexible film on your skin. It helps makeup and skincare products spread evenly, feel silky, and stay put longer. Because it's not absorbed into the skin, it sits on the surface and can help reduce water loss without clogging pores for most people.
What does Polymethylsilsesquioxane/Trimethylsiloxysilicate do in a beauty product?
When applied, it forms a uniform, breathable film that smooths the skin's surface, reduces the appearance of fine lines and pores, and helps other ingredients stay in place. It also provides a slight water-resistant barrier.
Is Polymethylsilsesquioxane/Trimethylsiloxysilicate safe for most people?
Polymethylsilsesquioxane/Trimethylsiloxysilicate is considered safe for cosmetic use at typical concentrations. It has low irritation and comedogenic potential, though individuals with very sensitive or dry skin may experience mild tightness. No serious safety concerns have been reported in regulatory reviews.
Who should be careful with Polymethylsilsesquioxane/Trimethylsiloxysilicate?
Those who prefer silicone-free or minimalist routines Individuals with very dry skin who may find film formers too tightening
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.