PEG, which is the abbreviation of polyethylene glycol, is not a definitive chemical entity in itself, but rather a mixture of compounds, of polymers that have been bonded together. Polyethylene is the most common form of plastic, and when combined with glycol, it becomes a thick and sticky liquid.
In cosmetics, PEGs function in three ways: as emollients (which help soften and lubricate the skin), as emulsifiers (which help water-based and oil-based ingredients mix properly), and as vehicles that help deliver other ingredients deeper into the skin.
As you may have noticed, PEGs are almost always followed by a number after their name, such as PEG 100. This number represents the approximate molecular weight of that compound. Typically, cosmetics use PEGs with smaller molecular weights. The lower the molecular weight, the easier it is for the compound to penetrate the skin.
The most important thing you need to know about PEGs is that they have a penetration enhancing effect, the magnitude of which is dependent upon a variety of variables. These include: both the structure and molecular weight of the PEG, other chemical constituents in the formula, and, most importantly, the overall health of the skin.
To note, independent of molecular size, PEGs of all sizes may penetrate through injured skin with compromised barrier function. So it is very important to avoid products with PEGs if your skin is not in tip top condition.
This penetration enhancing effect is important for three reasons: 1) If your skin care product contains a bunch of other undesirable ingredients, PEGs will make it easier for them to get down deep into your skin. 2) By altering the surface tension of the skin, PEGs may upset the natural moisture balance. 3) PEGs are not always pure, but often come contaminated with a host of toxic impurities.
Ethylene oxide (found in PEG-4, PEG-7, PEG4-dilaurate, and PEG 100) is highly toxic—even in small doses—and was used in World War I nerve gas.
And then there is 1,4-dioxane (found in PEG-6, PEG-8, PEG-32, PEG-75, PEG-150, PEG-14M, and PEG-20M), which, on top of being a known carcinogen, may also combine with atmospheric oxygen to form explosive peroxides—not exactly something you want going on your face.Information to come