What is Polyethylene Glycol (PEG)?
Polyethylene glycol (PEG) is found in many skin creams, lotions, soaps, hair products and shower gels. PEGs are petroleum-based compound that are often used as thickeners, solvents, softeners, and moisture-carriers. they have three main uses in cosmetics: as an emollient to help soften and moisturise the skin, as an emulsifiers to help oil and water-based ingredients mix together properly), and as a carrier that can help deliver other ingredients deeper into the skin.
In the ingredients list of a product it’s usually called PEG followed by a number e.g. PEG-400 or PEG 8000. This is because PEG is in fact a long chain of smaller ethylene glycol molecules stuck together. The number following PEG can either stand for how heavy the molecule is or how many ethylene glycol units make up the larger chain.
These ingredients are also used in many ways outside of cosmetics including medicine, food and some manufacturing processes. Different sizes are better at different jobs, in cosmetics you might use PEG 400 up to 8000 but they can go as high as PEG 180,000.
How does it work?
While PEGs are not so popular with consumers (see safety), they are popular with manufacturers as they make a great base for cosmetic products. They are soluble in water and can help less soluble ingredient dissolve as well. This means active ingredients that usually need to be in an oil based product can instead be used in an aqueous or water-based product. Their water binding potential gives the product a non-greasy, non-sticky texture and also acts as a humectant or moisturiser, actively holding onto the water it binds, stopping the product from drying out on your skin.
In soaps, hair products and shower gels, they act as plasticisers which lower the brittleness of the products and give it a silkier feeling.
Because things like melting point, viscosity and water retaining ability vary with the PEG’s size, a mix of different sizes can be used in one product to give the desired effect.
PEGs are unlikely to cause irritation or sensitisation of the skin unless the skin is damaged. As such it’s recommended that you avoid applying products containing these ingredients to broken or damaged skin.
Contamination of PEGs with the carcinogenic molecules ethylene oxide and 1,4-dioxane may occur as a by-product of PEG production, depending on the producer. While these molecules are dangerous, they are typically found in far too low a concentration to cause adverse effects according to an Environment Canada investigation.
Some studies have shown that they can carry unwanted substances across the skin barrier as well, especially if the skin barrier is compromised by a skin condition like eczema or injured.
Interactions with other medicine:
Some sizes of PEG can act as a penetration enhancer, increases the ability of certain molecules to cross the skin barrier and increasing the dosage received.
In general however PEGs in cosmetics are considered safe to use.
Other names for PEG:
PEG-4, PEG-6, PEG-7, PEG-8, PEG-9, PEG-10, PEG-12, PEG-14, PEG-16, PEG-18, PEG-20, PEG-32, PEG-33, PEG-40, PEG-45, PEG-55, PEG-60, PEG-75, PEG-80, PEG-90, PEG-100, PEG-135, PEG-150, PEG-180, PEG-200, PEG-220, PEG-240, PEG-350, PEG-400, PEG-500, PEG-800, PEG-2M, PEG-5M, PEG-7M, PEG-9M, PEG-14M, PEG-20M, PEG-23M, PEG-25M, PEG-45M, PEG-65M, PEG-90M, PEG-115M, PEG-160M, PEG-180M, Poly(oxyethylene), Carbowax, GoLYTELY, GlycoLax, Fortrans, TriLyte, Colyte, Halflytely, Macrogol, MiraLAX, MoviPrep