What it is
Polymethylsilsesquioxane is a silicone-based polymer supplied as fine spherical particles that act as a texturizing powder. The smooth microspheres impart a silky, silicone-like softness and a dry, smooth slip to formulas, and they create a soft-focus effect that can temporarily blur the look of fine lines and pores. In sunscreens it is valued for improving skin feel and helping reduce greasiness or shine.
Safety & warnings
As an inert spherical silicone powder that sits on the skin surface, polymethylsilsesquioxane is generally used as a well-tolerated texture and finish agent. It is common in primers, setting powders, and sun care, where it functions mechanically rather than as an active.
Origin & sourcing
It is a synthetic silicone resin belonging to the silsesquioxane family, organosilicon materials with the general formula RSiO1.5 that adopt cage-like or polymeric Si-O-Si structures. The cosmetic powder is formed by the hydrolysis and condensation of methyltrimethoxysilane, building the spherical methylsilsesquioxane particles.
Questions everyone asks
What does polymethylsilsesquioxane do?
It is a spherical silicone powder that adds a soft, silky slip, helps mattify the skin, and gives a soft-focus blurring effect.
Is it a silicone?
Yes. It is a silicone resin made from methyltrimethoxysilane, formed into tiny spherical beads.
Why is it in sunscreen?
It improves how the product feels and looks on skin, reducing shine and greasiness and smoothing the finish.