Peg

Polyethylene glycol (PEG) is a polyether compound made of repeating ethylene glycol units. Its general structure is HO-(CH2-CH2-O)n-H, and it is produced by polymerizing ethylene oxide with water. PEGs span a wide range of molecular weights, from about 200 to over 20,000 Da; low-molecular-weight grades are liquids, higher-molecular-weight grades are waxy solids or powders.

Properties include high water solubility, chemical stability, and low toxicity and immunogenicity. PEG chains can be end-functionalized to attach drugs, dyes, or proteins, enabling diverse applications in medicine and biotech.

Applications: In medicine, PEG is used as an osmotic laxative (for example PEG 3350) and as an excipient or solvent in injectable and oral formulations. PEGylation—attaching PEG chains to biologics—prolongs circulation time and can reduce immunogenicity. In research and industry, PEG is used to precipitate DNA, to promote protein crystallization, and as a lubricating or stabilizing additive in formulations and personal care products.

Safety and regulation: PEGs are widely regarded as safe for many uses, but contaminants such as residual ethylene oxide or 1,4-dioxane can be issues in some products. Some individuals may be sensitive to PEGs, so manufacturers screen for quality and impurities.

Other meanings: The acronym PEG also appears in finance as the price/earnings to growth ratio, a stock-valuation metric. The term PEG can have other, unrelated meanings in different fields, so context is important.