Propylene glycol is a synthetic liquid substance that absorbs water and hence is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products. Propylene glycol is also used to make polyester compounds, and as a base for de-icing solutions. It is used by the chemical, food, and pharmaceutical industries as an antifreeze when leakage might lead to contact with food. Propylene glycol is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions.