In the wake of the “free of” or clean beauty movement, many ingredients got a bad rep or seem to be controversial, to say the least. Even the longstanding classic ingredient vaseline got a crack in its reputation because it’s made from crude oil. Propylene glycol suffers the same end. First of all, it sounds so much like something from the chemistry class room and googling it only cements the chemical-y feeling.
But behind this obscure term hides one of the most common ingredients used in skin, hair, and personal care. And not only that. You can also find it in processed food and medications. It shares its roots with vaseline as it’s made also from petroleum. It also has been just as unfairly judged. Especially if you hear or read that it’s used as antifreeze …. wut? Antifreeze in my serum?! But rest assured, it’s safe, otherwise it wouldn’t be commonly found in food, medication, and skin care.
What it is
If you look at the molecular formula of propylene glycol, CH3CHOHCH2OH, you see that it has OH at one end. This makes it an alcohol.
It’s typically made by treating propylene oxide, a chemical produced from refining petroleum, with water.
The substance itself is a colourless, gloopy liquid. It’s almost odourless and has a faintly sweet taste. Since absorbs water and has hydrating and shooting properties, it’s added to all kinds of products such as toothpaste, sheet masks, shampoos, mascara, and more. It helps to improve the texture and stability of formulations as well as provide the skin with water, giving your skin that glowy, dewy look.
Uses
Propylene glycol is very versatile. It’s used in over 4000 products in the beauty industry but in very small amounts. It’s mainly used to help improve the texture and feel of products.
Other common uses are to enhance penetration into the skin so they can help other ingredients travel deeper into your skin. It helps to keep the product from melting at high temperatures or freezing at lower temperatures. So, propylene glycol retains the products’ natural vehicle formulation. It stops the formulation from changing consistency due to very high or low temperatures.
It’s also known as a fine humectant and helps to improve the water content of your skin. Completely soluble in water, it serves as a solvent to help dissolve ingredients that aren’t easily dissolved in water-based formulations. Lastly, it’s a mild antimicrobial and can help stop bacterial and other microbes to grow.
There you have it: propylene glycol is a multitasker, used as humectant, solvent, emulsifier, and preservative in many skin care products. It also helps deliver other ingredients. This means you end up with a more effective product with better texture and spreadability.
It should come as no wonder then, that it’s also used outside of cosmetics. It’s used in some foods to absorb extra water, maintain moisture, and provide solvent properties for some food colours and flavours. You can also find it as an emulsifier and emollient in medicine and even in tobacco products.
Propylene glycol is used as a preservative vehicle in topicals and some medications. Propylene glycol is an organic compound with multiple uses, including as a food additive, drug solvent, and a moisturizer in cosmetics, skincare, medicines, and tobacco products.
Other names it has if you want to find it on the ingredient list of your serum, hair conditioner, and what not:
- Trimethyl glycol
- Methyl ethyl glycol
- Dihydroxypropane
- 1,2-propanediol
So why the bad press?
There are a bunch of reasons why propylene glycol sounds scary and people try to avoid it.
The first is that it’s made of petrochemicals. Yeah, it’s understandable since it makes you think of crude oil, toxic waste, or carcinogenic. It’s also understandable given the climate effects of fossil fuels. Still, are you afraid of PET bottles and or polyester clothes? A lot of non-scary chemicals can be derived from petroleum. Almost all plastic is derived from petrochemicals.
The second is the term “anti-freeze”. In simple words, an anti-freeze is just a substance that can decrease the freezing point of water. So does salt, when you add it to water at freezing point (0 degrees Celcius). Sometimes, people confuse propylene glycol with ethylene glycol. Both are used as antifreeze, but ethylene glycol is a known toxin and not used in cosmetics.
Lastly, they can cause reactions and irritation. But that’s true with all chemicals. Depending on how you use a chemical, it can do completely different things. As with everything, it’s the dose that makes the poison. Moreover, propylene glycol is inert, or chemically inactive. In cosmetics, it’s used at low concentration, below 2%.
Is propylene glycol safe?
As a substance, propylene glycol is inert and so not bad for you or unsafe per se. It’s used so commonly as a humectant. It’s in a formulation to increase moisture retention in skin and hair.
Its ability to deliver ingredients into to skin means it’s a two-edged sword. On the one hand, it makes a product more potent since it helps the actives to better get into your skin. But on the other hand, it can mean that harmful toxins may also be able to permeate the skin where they would not normally be able to. These are then the culprit that can harm your lipid barrier and cause skin irritation.
Do you need to worry?
The FDA has rated propylene glycol as an additive that is “generally recognised as safe” for use in food. Even EWG that is always on the cautious side rates it at 3. On a side note, for the EWG, the lower the better.
So, unless you are sensitive to it, it’s not a cause for concern. Should you be sensitive, you’ll notice that products with large quantities might make your skin itchy and irritated.
You may have noticed that some brands start to replace it with 1,3-propanediol. This substance does the same jobs as propylene glycol but is made by fermenting cornstarch. The EWG gives it a low rating of 2. It’s thought to be safer than propylene glycol according to current data.
Regardless if you’re using one or the other, it’s always a good idea to observe your skin and see if it likes a new product.
