Polyethylene glycol (PEG) is a plastic. It is an organic polymer formed by polymerizing ethylene glycol. The repeating unit of the polymer is two carbons followed by an oxygen. PEG is edible and is used as a thickener in food and cosmetic products. PEG is edible and hydrophilic. Some medicines are "PEGylated" - have PEG attached to them - to make them more soluble or as a means of slowly releasing the drug into the body as the PEG chains are broken off.