DEG - Diethylene Glycol — Frequently Asked Questions

Because it is superficially indistinguishable from glycerine and propylene glycol. It is a clear, sweet, viscous liquid, it is cheaper, and unless it is specifically tested for it will pass visual and basic checks. That combination has led to repeated substitution in syrups and toothpaste, whether fraudulent or through inadequate testing, killing hundreds of people across several countries and decades.

It is metabolised to 2-hydroxyethoxyacetic acid and diglycolic acid, which cause acute kidney failure, and the lethal dose is small. Because the onset is delayed and the early symptoms are non-specific, poisoning is often not identified until multiple cases have accumulated, which is why the historical incidents have involved so many victims.

Pharmacopoeias require identity testing of every individual container of glycerine and propylene glycol received, not merely a check of the supplier's certificate. DEG must never be stored where it could be mistaken for those materials, and segregated, clearly labelled storage with separate handling equipment is appropriate given the consequences of an error.

Natural gas dehydration, unsaturated polyester and polyurethane manufacture, plasticisers, brake fluids and as an industrial solvent. It is a capable industrial material with real applications; the issue is entirely about ensuring it never reaches a route where it could be ingested, which means it is supplied for industrial use only.