Polyethylene glycol (PEG; /ˌpɒliˈɛθəlˌiːn ˈɡlaɪˌkɒl, -ˈɛθɪl-, -ˌkɔːl/) is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine.

[3] PEO's[clarification needed] have "very low single dose oral toxicity", on the order of tens of grams per kilogram of human body weight when ingested by mouth.

In the study, a high-sensitivity ELISA assay detected anti-PEG antibodies in 72% of random blood plasma samples collected from 1990 to 1999.

According to the study's authors, this result suggests that anti-PEG antibodies may be present, typically at low levels, in people who were never treated with PEGylated drugs.

[48] PEGs are prepared by polymerization of ethylene oxide and are commercially available over a wide range of molecular weights from 300 g/mol to 10,000,000 g/mol.

Very high-purity PEG has recently been shown to be crystalline, allowing the determination of a crystal structure by x-ray crystallography.

[49] Since purification and separation of pure oligomers is difficult, the price for this type of quality is often 10–1000 fold that of polydisperse PEG.

PEG is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, and is insoluble in diethyl ether and hexane.

It is, thus, imperative to assess potential PEG degradation to ensure that the final material does not contain undocumented contaminants that can introduce artifacts into experimental results.

They are used commercially in numerous applications, including foods, cosmetics, pharmaceutics, biomedicine, dispersing agents, solvents, ointments, suppository bases, as tablet excipients, and as laxatives.

Ethylene glycol and its oligomers are preferable as a starting material instead of water because they allow the creation of polymers with a low polydispersity (narrow molecular weight distribution).