What Is Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer?
Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer is a specialty silicone-based powder created by reacting methyltriethoxysilane with ethyl polysilicate in the presence of a small amount of tris-[3-(trimethoxysilyl)propyl]isocyanate, which links the two raw materials into a three-dimensional network. The result is an ultra-light, porous particle made mostly of silicon, oxygen, carbon and hydrogen.
Silicones first appeared in personal care in the 1950s, but this crosspolymer is a newer branch that became popular in the past two decades as formulators searched for ways to mimic the soft-focus finish of professional makeup. The ingredient is produced in a controlled hydrolysis and condensation process where the liquid silanes form solid spherical particles that are then filtered, washed and dried into a free-flowing powder.
You will usually find Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer in primers, foundations, color-correcting creams, pressed powders, blurring sticks, sunscreens, oil-control lotions, anti-aging serums and long-wear eye or lip products. Its airy structure lets it scatter light, soak up excess oil and leave skin with a velvety after-feel.
Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer’s Cosmetic Benefits/Uses
This ingredient is valued by formulators because it acts as a film former. By creating an invisible, flexible layer on the skin it helps makeup and skincare products stay in place longer, improves water and rub resistance, enhances spreadability and gives a smooth, soft-focus finish that can blur fine lines and uneven texture.
Who Can Use Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer
This silky silicone powder is generally considered suitable for all skin types. Oily and combination skin may especially welcome its oil absorbing and blurring abilities while dry and mature skin tend to appreciate the smooth glide it gives to creams and foundations without a tight or dehydrated feel. Sensitive skin usually tolerates it well because the particles sit on the surface and are chemically inert.
The material is synthesized from mineral derived silanes and contains no animal sourced components so it is appropriate for vegans and vegetarians. As with any cosmetic ingredient the finished product must also be cruelty free to meet individual ethical standards.
There is no published evidence that Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer poses a special risk to pregnant or breastfeeding women when used topically and in the small amounts found in cosmetics. This is not medical advice and anyone who is pregnant or nursing should show the full product ingredient list to a qualified healthcare provider before use just to be safe.
The ingredient is not known to cause photosensitivity nor does it interfere with sunscreen actives. It can be worn day or night and pairs well with most skincare actives since it mainly provides texture and film forming benefits rather than chemical activity.
Potential Side Effects/Adverse Reactions
Reactions to topical Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer vary from person to person. The points below outline potential side effects that may occur though most users will not experience any issues when the ingredient is properly formulated and used as directed.
- Mild redness or irritation in very sensitive skin
- Transient dryness if layered over strong exfoliating acids or retinoids
- Temporary clogged pores in individuals already prone to congestion when used in heavy, occlusive formulas
- Eye irritation if loose powder accidentally gets into the eyes
- Allergic contact dermatitis, a rare immune response to silicone materials
If any of these side effects occur stop using the product and seek advice from a healthcare professional or dermatologist.
Comedogenic Rating
Rating: 1/5
Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer is a large, crosslinked silicone powder that does not melt into pores or create an oily film. Its porous surface can even mop up a bit of excess sebum, so the likelihood of it blocking pores is very low. Occasional congestion may occur if the finished product contains other heavy ingredients or if it is applied in thick layers, but the polymer itself carries minimal risk.
Suitable for acne-prone and breakout-prone skin in most formulations.
Because it is an inert particle, it does not interact with sebum or bacteria, meaning any clogged pores are usually related to the total formula rather than to the crosspolymer alone.
Summary
Polymethylsilsesquioxane/Ethyl Polysillicate Crosspolymer is mainly a film former that creates a flexible, breathable layer on the skin, helping makeup and skincare last longer, resist water and rubbing, and deliver a smooth, soft-focus finish. Its porous structure also moderates shine and improves slip, so products spread easily without streaks.
While not as mainstream as basic dimethicone, this crosspolymer is steadily gaining popularity in primers, long-wear foundations and blur sticks because it offers extra oil control and a refined texture that consumers notice.
The ingredient is considered very safe for topical use with a low chance of irritation or pore blockage. As with any new cosmetic, perform a patch test when trying products that include it to ensure your skin agrees with the complete formula.