Pick up some of your skin or hair care products and chances are one of the ingredients will be a "Glycol". So let's demystify the "Glycols" so you will know just what they are and what they are doing in your favorite products.
Background So basically let's start with this. "Glycol" is the same thing as "Diol" and they both mean that the chemical structure of said ingredient contains two "-OH" groups (better known as a Hydroxyl group, the O is Oxygen (see red molecule in image), the H is Hydrogen). So what does that mean? Well, kinda nothing yet. Because there are oh so many different compounds with this double Hydroxyl group. So let's narrow our focus to the ones most likely to pop up in your products. Namely, Propylene Glycol (pictured), Butylene Glycol, and the famous PEG (Polyethylene Glycol). As for the latter, we see many ingredient lists with PEG in them, so now we know that PEG is really just short for another type of Glycol polymer. What are they doing in my products? Propylene Glycol, Butylene Glycol, and Polyethylene Glycol (PEG) are used as humectants, solubilizers, stabilizers, and to help increase product absorption into the skin. Many products have a ton of ingredients and without solubilizers/stabilizers (as well as emulsifiers, matrix creators, etc.) the products would be a clumpy, non-uniform, separated mess. Now that wouldn't sell, huh? Ok, so it's in there mostly to help the product formula come together basically, and with some added benefit of being a humectant (being able to draw in water i.e. to help moisturize) and to increase absorption.
Anti Freeze? To prevent it from liquefying at higher temperatures, or from solidifying at lower temperatures, the Glycols are added to help. As a side note, antifreeze is pure Propylene Glycol. Don't totally freak out though, the concentration of it in skincare products is much, much smaller, and not likely to be a major concern. But we'll cover that in a minute . . .
So what's the difference? Besides the chemical structure, not much. But what I want to cover relating to this blog, is their safety profiles. After reviewing scientific research and the MSDS data on all of these ingredients, it's pretty much safe to say, that out of all 3 listed Glycols above, only Propylene Glycol (yes, the one used to make antifreeze) has safety concerns that are worth noting.
As far as Butylene Glycol and the PEGs, there really is not much data indicating any toxic or irritant potential to be concerned about. However, for Propylene Glycol, it's well known (at high levels) to be very toxic and certainly fatal if ingested! And remember, it is absorbed by the skin!
What does this mean? Well, from previous posts, and ingredients in general, just because an ingredient itself has irritant/toxic potential in its purest, concentrated form, does not necessarily mean that it is not safe to use in personal products. That being said, I think it's wise to use ingredients that we know to be safer instead, hey, it's better to err on the side of caution isn't it?
Don't get all freaked out if your favorite product contains Propylene Glycol, there still is no reliable research showing it's not safe to use in skincare products (but also remember that this isn't easy to prove either way!). I would, however, stick to products, if given a choice, with one of the other Glycols instead.
The other concern is the absorption of these ingredients. Remember, when you see these ingredients in your skincare, it means that they may actually help your skin absorb the other ingredients in the product as well. So if there's a bunch of ingredients in the product you are using that are "yucky" or you wouldn't want to be absorbed into your skin, well, than just note that their absorption can, in fact, be increased with the addition of these Glycols.
Hey, remember, I can't tell you for sure whether to use certain products or ingredients all the time, just simply due to the fact that science hasn't gotten around to proving the safety/toxicity or long-term effects of many of these ingredients. But what I hope to do is just to get the thinking process started, so that we can simply be aware of what these ingredients are, their indirect/direct safety profiles, and how they work with other ingredients. After all it's all about being a wiser consumer, especially when it comes to products that you apply (and will be absorbed) by the body! Remember, if there are definitely research outcomes proving the dangers of any skincare ingredients, I will certainly try and cover them here on Truth in Skincare!