PEGs (polyethylene glycols) function as:
- emollients (which help soften and lubricate the skin),
- emulsifiers (which help water-based and oil-based ingredients mix properly),
- vehicles that help deliver other ingredients deeper into the skin.
Skin penetration enhancing effects have been shown with PEG-2 and PEG-9 stearate.
Polyethylene when it is not combined with glycol, is the most common form of plastic used in the world. It is flexible and has a smooth, waxy feel. When ground up, the small particles are included in scrubs as a gentle abrasive. When mixed with glycol, it becomes a viscous liquid. In the minuscule amounts used in cosmetics, 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 the skin. It is also used internally in medical procedures to flush and clean the intestinal tract. – Beautypedia
Various forms of PEG-compounds are mixed with fatty acids and fatty alcohols to create a variety of substances that have diverse functions in cosmetics, including acting as surfactants, binding agents (to keep ingredients blended), stabilizers, and emollients. – Beautypedia