What it is
This is a polyether-modified silicone (a dimethicone copolyol) bearing two PEG-15 methyl ether grafts that make an otherwise water-incompatible silicone able to interact with water. In sunscreens it works mainly as an emulsifier and co-emulsifier, stabilizing silicone-in-water or water-in-silicone systems and improving spreadability. It also contributes a smooth, silky after-feel and can help disperse other silicone components.
Safety & warnings
PEG/dimethicone copolymers of this kind are generally considered low-irritation and non-sensitizing surfactants. They are large, substantive molecules with limited skin penetration, and they are not typically flagged as comedogenic.
Origin & sourcing
Synthetic, made by attaching polyethylene glycol (methyl-capped) chains to a dimethicone backbone.
Questions everyone asks
Why combine PEG with silicone?
The PEG chains make the silicone water-compatible, so it can emulsify and stabilize formulas that mix silicone and water phases.
Is it an emulsifier or an emollient?
Primarily an emulsifier and surfactant, though it also lends a light silicone-like skin feel.