- Propylene glycol is a synthetic, organic compound with the chemical formula C₃H₈O₂. It is a clear, colorless, odorless, and slightly viscous liquid that is highly soluble in water, alcohol, and many organic solvents.
- Propylene glycol is classified as a diol, meaning it contains two hydroxyl (-OH) groups, which contribute to its hygroscopic (moisture-attracting) and solvent properties. It is widely used across various industries, including food, pharmaceuticals, cosmetics, and industrial manufacturing, due to its versatility, low toxicity, and ability to mix with both hydrophilic and hydrophobic substances.
- In the food industry, propylene glycol serves as a humectant, solvent, emulsifier, and preservative. It is commonly found in processed foods, beverages, flavor extracts, food colorings, and frostings. As a humectant, it helps retain moisture and improve texture, while as a solvent, it aids in dissolving flavors and food additives evenly. The U.S. Food and Drug Administration (FDA) has classified propylene glycol as “Generally Recognized as Safe” (GRAS) for use in food products at specified concentrations, although intake should be within established safety limits.
- In pharmaceuticals, propylene glycol is used as a solvent or carrier for both oral and topical medications, as well as in injectable formulations. It helps dissolve active ingredients that are poorly soluble in water and ensures consistent delivery of the drug. In topical and personal care products—such as creams, lotions, shampoos, and deodorants—it functions as a moisturizer and skin-conditioning agent, thanks to its ability to draw water into the skin. It also contributes to the stability and texture of these formulations, enhancing their spreadability and shelf life.
- In the cosmetic and personal care sector, propylene glycol is valued for its moisturizing and emollient properties. It helps to prevent the drying out of creams and gels and improves the absorption of active ingredients into the skin. Despite its widespread use, some individuals may experience mild skin irritation or allergic reactions, particularly with prolonged exposure or high concentrations. However, such reactions are relatively rare, and propylene glycol is considered safe for most skin types when used in regulated amounts.
- Beyond consumer products, propylene glycol is used in industrial and commercial applications. It serves as an antifreeze agent in situations where a non-toxic alternative to ethylene glycol is needed—such as in HVAC systems, food processing equipment, and recreational vehicle plumbing. It also plays a role in the manufacture of plastics, resins, and paints, and is used in the production of fog or smoke effects in theatrical and firefighting training environments.
- Although propylene glycol is metabolized by the liver and excreted via the kidneys, concerns have been raised about its use in high doses or in sensitive populations, such as infants or people with compromised kidney function. Toxicity is extremely rare and generally associated only with excessive or inappropriate medical use.
