When it comes to the medical science and the internet, we really should be taking everything with a grain of salt. For some people though, an article merely questioning an ingredient means it's out of their skincare rotation. Others might need a little more convincing before they begin the hunt to replace a beloved beauty product. Take for example, propylene glycol. A quick internet search will populate with terms like "carcinogenic," "toxic," and "antifreeze"—not exactly what you want to read about an ingredient commonly found in your skincare products.

To clear up some very serious claims, we turned to three board-certified dermatologists to find out the possible pros and cons of propylene glycol, and how clean it really is, Keep reading so you can make your own informed decision about whether or not to continue using products containing this skincare ingredient.

Meet the Expert

• Jennifer Herrmann, MD, FAAD, is a board-certified dermatologist based in Beverly Hills.
• Joshua Zeichner, MD, is a board-certified dermatologist and the director of cosmetic research in dermatology at Mount Sinai Medical Center.
• Lauren Penzi, MD, is a board-certified dermatologist who specializes in medical and cosmetic dermatology.

What Is Propylene Glycol?

Propylene glycol is a colorless, odorless liquid that is completely water-soluble. According to board-certified dermatologist Dr. Jennifer 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.

Propylene Glycol

Type of ingredient: Humectant, solvent, emollient, and preservative.

Main benefits: Attracts water and locks it into the skin.

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.

Benefits of Propylene Glycol for Skin

"Propylene glycol is a common ingredient that is used as a vehicle for different cosmetics and therapeutics, usually as an emollient and an emulsifier," says board-certified dermatologist Dr. Lauren Penzi of the versatile ingredient. Here are its main functions:

• Attracts water: Board-certified dermatologist Dr. Joshua 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.
• Boosts other ingredients: Because of its binding properties, propylene glycol can enhance the delivery of other active ingredients into the skin.
• 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."
• 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.
• Is safe for acne-prone skin: Because it’s not oily, Herrmann says it’s also ideal for those with acne.
• Helps lessen the appearance of spots over time: Due to its moisturizing properties, propylene glycol nourishes the skin, helping to lessen the appearance of marks and acne spots.

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." Penzi adds that it has a tendency to "induce irritation and even true allergic skin reactions, causing redness, flaking, burning, etc." "It can also be comedogenic, meaning it can clog the pores and cause an acne outbreak," she says.

Although propylene glycol is overall safe, sensitive skin types should proceed with caution. "For my eczema prone patients, I recommend first doing an at home patch test by applying the product to the inner wrist or forearm for a few days, before applying it to a sensitive area like the face. For those who have been patch tested with a dermatologist and have a known true allergic contact dermatitis to propylene glycol, certainly all these products should be fully avoided," says Penzi.

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 used in relatively large quantities.

FAQ

• Yes. Because it helps bind water to the skin, it can be extra beneficial for those who struggle to retain moisture.

• Because it’s not an oily ingredient, propylene glycol is also beneficial for those with acne-prone skin.

• Propylene glycol is most commonly used in creams, lotions, and serums.

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