Propylene Glycol (C3H8O2) CAS# 57-55-6 Propylene Glycol is a compound usually as a tasteless, odorless clear liquid, determined by the Food and Drug Administration (FDA) to be "generally recognized as safe" for use in food, cosmetics, and medicines. Propylene Glycol is used to store/retain moisture in foods and other products. The compound is also used to make artificial smoke for use in firefighter's training and theatrical productions. Often mistaken for Ethylene Glycol (a toxic ingredient in common automotive coolant/antifreeze), Proplylene Glycol is non-toxic to humans and labaratory animals even in elevated amounts. However, similar to Ethylene Glycol, Propylene Glycol raises the body's acidity.