What it is
This is a dimethicone (silicone) backbone modified with short polyethylene-glycol chains, which makes the silicone partly water-compatible. The resulting molecule works as a nonionic silicone emulsifier, helping stabilize water-in-silicone or water-in-oil systems common in sunscreens, and also imparts a smooth, silky skin feel. It is frequently used to help disperse pigments and inorganic UV filters evenly.
Safety & warnings
Silicone-based PEG emulsifiers like this are generally well tolerated and low in irritation potential. As an ethoxylated material, supplier purification controls trace ethylene oxide and 1,4-dioxane. It is not regarded as comedogenic at usual use levels and is widely used in leave-on facial products.
Origin & sourcing
Synthetic; a silicone polymer (dimethicone) chemically modified with polyethylene glycol.
Questions everyone asks
Why is PEG-3 Dimethicone used in sunscreens?
It emulsifies and stabilizes water-in-silicone formulas and helps disperse inorganic UV filters and pigments evenly while giving a smooth feel.
Is it a silicone or a PEG?
It is both: a silicone backbone modified with PEG chains, which gives it the slip of silicone and the water compatibility of a PEG surfactant.