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Do a quick internet search on propylene glycol, and your results will be inundated with red flags like, "carcinogenic," "toxic," and "antifreeze"—not exactly what you want to read about an ingredient commonly found in your skincare products. (It's also found in food and other products, but for the interest of this article, we'll stick to skincare.) Then again, the internet is a lawless land full of misinformation and conflicting opinions, so how much can we really believe to be true? For some, even questionable ingredients are out of the question, but others might need a little more convincing about an ingredient's harm before they toss out their beloved beauty products.
To clear up some very serious claims, we turned to board-certified dermatologists Jennifer Herrmann, MD, FAAD, and Joshua Zeichner, MD, the director of cosmetic research in dermatology at Mount Sinai Medical Center. Keep reading to find out the possible pros and cons of propylene glycol so you can make your own informed decision about whether to continue using products containing the skincare ingredient or not.
Type of ingredient: Humectant, Solvent, Emollient, and Preservative.
Main benefits: Retains moisture, Preserves the formula, and Dissolves ingredients.
Who should use it: In general, anyone who is looking for extra hydration and smoothness of the skin.
How often can you use it: Propylene glycol is a safe ingredient to use regularly, provided that you do not have an allergy to it.
Works well with: Because it has so many functions, there isn’t a specific list of ingredients that it works well with.
Don't use with: Propylene glycol works well with most, if not all, ingredients.
What Is Propylene Glycol?
Propylene glycol is a colorless, odorless liquid that is completely water-soluble. According to Herrmann, it is synthetic and produced by adding water to propylene oxide, which is derived from petroleum products. Propylene glycol is used as a humectant, a preservative, a solvent, or an emollient in a wide variety of formulas, such as creams, lotions, serums, shampoos and many other types of personal care products.
Benefits of Propylene Glycol for Skin
Propylene glycol has many functions and is used in a multitude of skincare products for its versatility. Here are its main functions:
- Attracts water: Zeichner says at low concentrations, propylene glycol acts like a humectant, which means it binds water and pulls in hydration to the outer skin layer. When used in cosmetic products, it helps give the skin a hydrated, dewy appearance.
- Lightly moisturizes: Herrmann adds that as a humectant, it also offers moisturizing benefits and smoothes the skin with a light, non-sticky feel.
- Addresses visible signs of aging: The humectant property also makes it a useful ingredient for dry or aged skin. "As we age, our skin loses a component called Natural Moisturizing Factor (NMF) and subsequently dries out, which emphasizes wrinkles and contributes to flaking and roughness," Herrmann says. "Propylene glycol helps bind water from the environment, helping to counter the water loss that accompanies aging."
- Dissolves ingredients: Herrmann says as a solvent, it helps dissolve ingredients, such as salicylic acid, ferulic acid, allantoin, and vitamin C, into products. She adds that it's especially beneficial for ingredients that are difficult to dissolve into creams and serums, like fragrances and pigments.
- Enhances penetration: Zeichner says it helps the active ingredients of cosmetics penetrate through the skin, which in turn makes them more effective.
- Prevents water loss: As an emollient, propylene glycol forms a protective film on the skin that prevents water loss and helps to smooth and soften skin, according to Herrmann.
- Preserves the formula: Propylene glycol is antimicrobial, and Zeichner says at higher concentrations, it acts as a preservative to prevent contamination.
- Is safe for acne-prone skin: Because it’s not oily, Herrmann says it’s also ideal for those with acne.
Propylene Glycol vs. Ethylene Glycol
Though commonly confused for each other, propylene glycol and ethylene glycol are structurally different, and it's important to distinguish the two. According to Herrmann, ethylene glycol (an ingredient used in antifreeze) is considered to be toxic and harmful, while propylene glycol is not.
Side Effects of Propylene Glycol
While propylene glycol actually should be avoided for some people, it's not for the scary reasons you might have read about online. Because propylene glycol is derived from petroleum, many have concerns that it is carcinogenic and can be toxic when used in skincare. But according to Zeichner, cosmetic-grade petrolatum is different than commercial petroleum and is not carcinogenic, and similarly, neither is propylene glycol. Herrmann adds, "Many safe products and chemicals can be derived from toxic parents, but what matters for safety is the final chemical structure form. She continues, "Unless contamination is an issue, being derived from petroleum doesn’t make it dangerous. Its final form is considered non-carcinogenic and is found in many topical cosmetic products."
While there's no truth to these more serious claims, propylene glycol isn't totally innocuous either. As Herrmann points out, it was the American Contact Dermatitis Society's Allergen of the Year in 2018. "If you are developing a red, itchy rash where you’re applying your product, you may have an allergy to one of its ingredients," Zeichner says. "Propylene glycol is often the culprit." Herrmann adds that those with eczema might be more likely to be sensitive to the ingredient, and for those patients, she always suggests patch tests or trying new products on a small area of the skin on the inner wrist before applying them more broadly.
In general, however, products containing propylene glycol are fine to use for most people. "Based on what we know today and based on years of use in cosmetic products, propylene glycol is a safe ingredient to use, provided that you do not have an allergy to it," Zeichner says.
How to Use It
As Herrmann explains it, because propylene glycol is in so many products, there isn’t one way to use it. Instead, she recommends using products containing the ingredient as directed by your dermatologist or as instructed by the manufacturers. As far as how often you should use it or how much should be used, Herrmann says propylene glycol is considered safe, even when consumed in relatively large quantities.
The Best Products With Propylene Glycol
Paula’s Choice is known for its effective products and no-BS approach to skincare, so it should come as no surprise that this acne treatment is one of Herrmann's top picks. “Propylene glycol helps increase hydration without being oily and helps the benzoyl peroxide penetrate pores more deeply and effectively,” Herrmann says.
Another favorite of Herrmann's, this oil-free cleanser contains 8.5% glycolic acid to exfoliate and brighten skin, while camellia and licorice extracts relieve any redness and inflammation. “Propylene glycol keeps it light and ideal for blemish-prone skin," she adds.
Dermatologists, beauty editors, and skinfluencers swoon over SkinCeutical's products, and Herrmann highly suggests giving this serum from the line a try if you haven't yet. “It’s packed with antioxidants to help keep skin’s DNA healthy and boost collagen production,” Herrmann says. “It also contains light alpha-hydroxy acids that lightly exfoliate and maximize radiance.” Did we mention it contains propylene glycol to boost its penetration?
Another favorite of dermatologists and beauty editors alike, this moisturizer uses a combination of ceramides, sodium hyaluronate, and propylene glycol to replenish the skin's moisture levels and seal that hydration for healthy, supple skin.
You can count on the combination of ferulic acid, retinol, and licorice root extract in this product (which made Byrdie's list of the best eye serums) to stop the damage caused by extrinsic aging that can result in wrinkles and discoloration. And with propylene glycol, these ingredients can better penetrate the skin and work more effectively.
This serum makes almost every retinol product roundup for good reason: It works without destroying your skin. Milder than most retinol serums, this formula relies on retinyl palmitate to gently boost cellular turnover and is a great alternative for those with sensitive skin. The soothing properties of aloe vera and the hydration of the propylene glycol also work to counteract the dryness and irritation often caused by retinoids. It even made one retinol-opposed Byrdie editor a believer.
It might not be a skincare product, but this formula is one of Herrmann's top product recommendations and deserves a mention on this list anyway. Much like it does for your skin, propylene glycol works to hydrate the hair sans sticky feel. "Propylene glycol helps this shampoo hydrate hair by binding water and prevents its evaporation," Herrmann says. "Because it’s light, it also doesn’t cause buildup like some oil-containing shampoos."