Polypropylene glycol is a nontoxic, odorless, clear and colorless liquid that is used extensively in food, pharmaceutical and cosmetic industries as a direct and indirect additive. The liquid has low vapor pressure and viscosity. Commercial polypropylene glycol is commonly made from water and propylene oxide obtained from organic and inorganic sources.
The United States Food and Drug Administration has given polypropylene glycol the GRAS (generally recognized as safe) status because it is easily metabolized in the human body as a carbohydrate. It is available in several grades. Industrial grade polypropylene glycol is used as an engine coolant and antifreeze. The food and the pharmaceutical grades have been in use for over 50 years. The inert chemical serves as a solvent and a stabilizer as it does not react or alter the ingredients of the final product. In the cosmetic industry, polypropylene glycol is also used as a moisturizer and as a fragrance dispenser.