Also listed as PEG on ingredient labels, it helps keep products stable and performs functions similar to those of glycerin. Because polyethylene glycol can penetrate skin, it is also a vehicle that helps deliver other ingredients deeper into skin. Polyethylene glycol as used in cosmetics is purified for safety.
Reference for this information:
Drug Delivery, October 2016, pages 3,101-3,110
Toxicology, October 2005, pages 1-38