Polyethylene glycol (PEG) is a hydrophilic synthetic compound with a wide range of commercial applications. The chemical’s ability to absorb water means it’s often used in cosmetic products, where it acts as a cleansing agent, skin conditioner, and emulsifier. PEG is also a common ingredient in parenteral medications and laxatives.
Continue reading to learn more about the common uses of polyethylene glycol, along with the potential dangers.
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What is polyethylene glycol?
Polyethylene glycol is a polymer derived from a petroleum compound called ethylene oxide. A glycol, meanwhile, is essentially an alcohol with two hydroxyl groups attached to two adjacent carbon atoms.
The simplest glycol is ethylene glycol, which is primarily used as an antifreeze. However, unlike ethylene glycol, PEG is generally considered non-toxic.
Although the specific number of molecular chains in a PEG compound can vary, they can be generalised using this chemical formula:
C2nH4n+2On+1
As you can see, for every double the amount (n) of carbon, there is four times the number of hydrogen plus two, and one amount of oxygen plus one.
Classed as an oligomer, polyethylene glycol has a colourless appearance, a viscous consistency, and an odourless smell. Its hydrophilic properties make it suitable for use in many different products including medicines, cosmetics, and reusable plastic bags.
6 common uses of polyethylene glycol
From cosmetics to rocket fuel, PEG has a wide variety of applications. Some common uses of polyethylene glycol are summarised below, but there are many more.
1. Medical tools & devices
Polyethylene glycol has various medical applications covering both diagnosis and treatment. For example, it’s commonly used as an excipient or non-active ingredient in many topical, oral, and parenteral medications.
PEG is also present in some laxative medications that are designed to treat children’s constipation. Meanwhile, whole bowel irrigation with a polyethylene glycol solution is commonly performed to flush the gastrointestinal tract before a colonoscopy or surgery.
When it comes to diagnostics, PEG can help to detect antibodies and antigens in blood analysis. As an excipient, PEGylated lipid plays an important role in the manufacture of SARS-CoV-2 vaccines. The mRNA in these vaccines are encapsulated in bubbles of lipids.
2. Cosmetics
Another major use of polyethylene glycol is in the manufacture of cosmetic products like shampoo and shower gel. That’s because PEG’s hydrophilic properties make it an ideal surfactant and emulsifier. The chemical is also a common ingredient in moisturisers and conditioning products.
3. Ceramics binders
PEG is often used as a binder in advanced ceramic production. The substance is mixed with alumina granules and spray-dried on ceramic surfaces or layers, which are then bonded together under pressure and heat.
4. Clear product packaging
Polyethylene glycol can be synthesised into polyethylene glycol terephthalate (PET or PETE) – a highly glossy and transparent plastic that’s often used as packaging material for various products. PET is also used to make medical tubes, cosmetic containers and electronics packaging.
5. Supermarket carrier bags
With single-use plastic carrier bags in decline, stronger, and more eco-friendly alternatives are now commonplace in UK supermarkets. Made from tough plastic fibres, these reusable carriers are normally produced using polyethylene glycol.
6. Military use
Polyethylene glycol can also be plasticised using nitrate ester to form a solid propellant known as NEPE-75. This fuel is used in submarine-launched ballistic missiles.
Is polyethylene glycol bad for the environment?
Polyethylene glycol is biodegradable and non-toxic to marine organisms. As a result, it’s generally considered non-harmful or, at the least, very low risk to the environment.
That said, some variations and derivatives of this polymer (particularly plastics) may have negative environmental impacts.
The dangers of polyethylene glycol
Although PEG is generally a safe and biodegradable compound, the chemical can be dangerous to anyone who develops an extreme allergic reaction to it (although this is very rare).
Some of the derivatives and variations of polyethylene glycol may also have potentially adverse effects. For example, the over-the-counter laxative medication polyethylene glycol 3350, or Miralax, can cause nausea, bloating, and diarrhoea.
Summary
Polyethylene glycol, or PEG, has a wide range of commercial, industrial and medical applications. The compound is either used as an active ingredient, an excipient, or a precursor to other chemical products such as plastics.
PEG is commonly used to make cosmetic goods, pharmaceutical products and reusable plastic bags. On its own, the substance is biodegradable and non-toxic. Although polyethylene glycol is generally considered safe, some people can develop anaphylaxis or have an extreme allergic reaction to it.
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