What Is Propylene Glycol?
Propylene Glycol (C₃H₈O₂, MW ≈ 76 g/mol) is a colorless, nearly odorless, slightly sweet, hygroscopic liquid that blends well with water and most organic solvents. It melts at about –60 °C and boils around 187–188 °C. Produced primarily via hydration of propylene oxide—and more recently via bio‑derived pathways—it sees global demand approaching 2 million tonnes per year, likely doubling by 2035 East India Chemicals.
Key Industries and Applications
1. Food & Beverage
Propylene Glycol (E‑number E1520) is widely used as a humectant, stabilizer, emulsifier, and flavor/color carrier in processed foods, baked goods, beverages, frozen desserts, and dressings. It’s FDA‑approved up to defined limits (e.g. 2% in general foods; 2.5% in frozen dairy; up to 24% in frostings; 97% in seasonings/flavorings). EFSA sets an acceptable daily intake of about 25 mg/kg body weight Wikipedia+1Vizag Chemicals+1.
2. Pharmaceuticals & Medical
PG serves as a solvent, stabilizer, and carrier in oral, topical, and injectable formulations—including syrups, ointments, creams, and IV products. It’s also used in cough syrups to dissolve active ingredients evenly and protect them from degradation Elchemy. However, major safety incidents—like WHO‑reported batches of contaminated propylene glycol mislabeled with ethylene glycol, linked to child fatalities in Pakistan and elsewhere—underscore the critical importance of ensuring high‑purity pharmaceutical (USP) grade supply Reuters+1Wikipedia+1.
3. Cosmetics & Personal Care
Cogent as a humectant, emollient, and penetration enhancer, PG is found extensively in lotions, shampoos, deodorants, serums, and cleansers. It helps deliver active ingredients deeper into the skin while maintaining smooth texture ElchemyChemicalBookWikipedia. While cosmetic‑grade PG is generally recognized as safe, sensitive individuals may experience contact dermatitis or acne, sometimes identified as American Contact Dermatitis Society’s Allergen of the Year in 2018 Byrdie+1Wikipedia+1.
4. Industrial & Technical Uses
PG is valued in industrial settings for:
- Antifreeze and coolant fluids (HVAC systems, glycol chillers, refrigeration, automotive, and food-processing equipment). Its low toxicity and biodegradability make it a safer alternative to ethylene glycol East India Chemicals+15ESSELTHERM+15Raw Source+15.
- Heat transfer fluid: Used in glycol chiller systems for breweries, cold storage, solar thermal installations, etc. USP-grade PG is essential for food or pharmaceutical environments ESSELTHERMWikipedia.
- Paints, coatings, inks, plastics and polyester resins: Acts as a viscosity modifier, solvent, and plasticizer in manufacturing of composites, adhesives, and printed media Raw Source.
- De-icing and fog effects: Used in aircraft deicing fluids and theatrical smoke/fog machines due to its low freezing point and safe profile compared to ethylene glycol ScienceDirect+2Wikipedia+2Vizag Chemicals+2.
It also finds niche use in textiles, agriculture (pesticide formulations/additives), pet food, and cryopreservation solutions Raw Source.
Safety and Regulatory Notes
Regulated as GRAS by the FDA, PG is deemed safe for use in foods, cosmetics, and pharmaceuticals when used within prescribed limits ESSELTHERM. Overexposure risks include skin irritation, allergic contact dermatitis, and, in rare cases, systemic effects like lactic acidosis following IV administration in neonates or burn patients ChemicalBook.
Notably, contaminated industrial-grade PG sold as pharmaceutical-grade has been linked to serious health incidents—including child fatalities via contaminated cough syrups—prompting tighter regulations in exporting countries, including mandatory pre-export testing of cough syrups from India Reuters+1Wikipedia+1.
Conclusion
Propylene Glycol is a highly versatile, generally safe chemical used across food, pharma, personal care, and industrial sectors. Its moisture-retention, solvent properties, and favorable toxicity profile make it essential in modern formulations. However, quality control, proper grade selection, and adherence to regulatory thresholds are mandatory to ensure safety and efficacy—especially in medical and food-grade applications.