Propylene glycol, also known as 1,2-propanediol, is a synthetic (i.e., man-made) alcohol that attracts/absorbs water. It is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Propylene glycol is one of the most widely used ingredients in cosmetics and personal care products, including facial cleansers, moisturizers, bath soaps, shampoos and conditioners, deodorants, shaving preparations, and fragrances. In addition to its use as an ingredient in cosmetic and personal care products, it is used in numerous food items such as beer, packaged baked goods, frozen dairy products, margarine, coffee, nuts, and soda. It is also used as an inactive ingredient (e.g., solvent) in many drugs. FDA has approved its use at concentrations as high as 98% in drugs applied to the skin and 92% in drugs taken orally.

Because propylene glycol attracts water it functions as a humectant and is used in moisturizers to enhance the appearance of skin by reducing flaking and restoring suppleness. Other reported uses include skin-conditioning agent, viscosity-decreasing agent, solvent, and fragrance ingredient.

Propylene glycol was reported to be used in 14,395 products, according to 2019 data in U.S. FDA’s Voluntary Cosmetic Registration Program (VCRP).