Propylene glycol is an odorless, colorless liquid used in the manufacture of consumer and industrial products. Generally recognized as safe (GRAS), the U.S. Food and Drug Administration (FDA) approves its use as an indirect food additive. Propylene glycol is also used in cosmetics, pharmaceuticals, and a wide range of other practical applications, according to the Dow website. Pharmaceutical-grade and industrial-grade are the two grades used.
Pharmaceutical-grade propylene glycol USP/EP is used as a non-active enabling agent, also known as an excipient. As an agent, it carries flavors in food and beverages, helps retain taste and moisture in pet and livestock feed, and acts as a carrier of active ingredients found in cough syrup and gel capsules. Propylene glycol keeps personal care products consistent, soft and moist. This includes deodorant sticks, sunscreen, shampoos, body lotions, face creams and lipstick. Additionally, it works as an excipient to stabilize foam in personal care and health care products.
Industrial-grade propylene glycol is used in industries as a heat-transfer medium that protects against pressure burst and corrosion, controls viscosity, and dissolves active agents. Industrial propylene glycol is also used in paints and coatings for wear and weather protection, as an aircraft de-icer, in liquid detergents, antifreeze, and as a solvent in printing ink. As a basic building block, it is used in its raw form to make formable plastics like unsaturated polyester resins. The resins are used in windmill blades, furniture, marine construction, gel coats, synthetic marble coatings, sheet molding compound and for heavy impact surfaces such as floors.
For medicinal purposes, propylene glycol is used as a solvent in different formats: injectable, oral and topical. For injectable medications, 40 percent is made of propylene glycol. Adverse effects are not likely to occur with normal use; however, heavy use of injectable medication, or extensive topical uses on compromised skin, like burns, has resulted in excess levels of propylene glycol in the body which can cause toxicity, according to the Center for Disease Control (CDC) website.
Aerolized forms of propylene glycol are used to create a dense "smoke" without flames. The aerolized products is used by the United States military as a smokescreen to hide the movements of troops on the battlefield. Additionally, the product is also used to simulate smoke in different types of fire-training procedures as well as theater productions, according to the CDC.
The greatest amount of propylene glycol is found in the textile industry where it is used in polyester fiber production. For military dietary rations, propylene gycol is an FDA-approved additive, according to the CDC.