Liz deSousa for BYRDIE
There are hundreds upon thousands of ingredients used in beauty products. And while we've seen a trend in recent years of more natural and minimal labels, there are some synthetic ingredients that we just can't do without. Take for example propanediol, the overachieving solvent, humectant, and emollient wrapped in one. Propanediol is an excellent substitute for propylene glycol, which, although has been determined to be safe when used in skincare, we can't forget that it was named the American Contact Dermatitis Society's Allergen of the Year back in 2018 due to its bad rap for causing contact dermatitis. If you have adverse reactions to propylene glycol, or are looking for a better alternative that is safer for your skin, propanediol might be for you.
Although the two are very similar, there are some key distinctions that could make propanediol a better option for you. To find out more on propanediol and how it differs from propylene glycol, we interviewed two board-certified dermatologists and a cosmetic chemist.
Meet the Expert
- Sapna Palep, MD, is a board-certified dermatologist of Spring Street Dermatology in NYC.
- Marisa Garshick, MD, FAAD, is a board-certified dermatologist at MDCS Dermatology.
- Michelle Wong, PhD, is a cosmetic chemist and content creator at Lab Muffin Beauty Science.
Keep reading for more information before making the switch from propylene glycol to propanediol in your skincare.
Propanediol
Type of ingredient: Solvent, humectant, and emollient
Main benefits: Dissolves ingredients, decreases viscosity, and retains moisture
Who should use it: Generally, anyone looking for an alternative to propylene glycol in their skincare.
How often can you use it: Propanediol is a safe ingredient to use regularly, provided that you do not have a sensitivity to it.
Works well with: Because of its wide range of uses, propanediol does not function especially well with any ingredient in particular.
Don't use with: According to dermatologists, propanediol works well with most, if not all, ingredients.
What Is Propanediol?
Technically speaking, propanediol is a three-carbon diol and a colorless viscous liquid that is miscible (or mixible) with water. Since it's derived from corn sugar, dermatologist Dr. Sapna Palep describes propanediol as a natural alternative to propylene glycol. According to dermatologist Dr. Marisa Garshick, propanediol is "a preservative used in various cosmetic and personal care products." such as lotions, cleansers, toners, and other topical skin treatments. A bit of an overachiever, propanediol can function as a solvent, humectant, and even an emollient when used in skincare.
Benefits of Propanediol for Skin
The reason you can spot propanediol on so many different product labels is due to its versatility. Although Palep says it primarily functions as a solvent, propanediol also has impressive sensory qualities and various other benefits when used in skincare:
- Dissolves ingredients: According to Palep, propanediol is considered to be an excellent solvent for harder to dissolve ingredients, like salicylic acid or ferulic acid, for instance.
- Decreases viscosity: As Palep explains it, a viscosity reducer is helpful in a variety of cosmetics, like conditioner, shampoo, foundation, mascara, body wash, hair spray, cleanser, and moisturizer, because it allows the formulas to flow well and makes them easier to use on the skin and hair.
- Improves humectancy: As a humectant hair and skin conditioner, propanediol pulls moisture into the skin and encourages water retention.
- Prevents water loss: Thanks to its emollient properties, propanediol might soften and smooth skin by reducing water loss.
- Safe for acne-prone skin: According to Palep, foam cleansers tend to use fewer surfactants (the cleansing chemicals that remove dirt and oil from your skin), which may make them ideal for acne-prone or sensitive skin types. Propanediol can increase foaming in a product, so those prone to breakouts might prefer products containing the ingredient for that reason.
- Enhances preservative efficacy: Palep adds that propanediol can also function as a preservative booster in skincare products.
- Gives the product a lightweight feel: Not only does propanediol contribute to the function of a product but also its consistency. Palep says the ingredient gives products a light texture and a non-sticky feel.
Propanediol vs. Propylene Glycol
"It [Propanediol] has become increasingly popular as an alternative to propylene glycol, which may cause skin irritation and sensitivity in some individuals," says Garshick. It's easy to see how 1,2-Propanediol and 1,3-Propanediol (aka propylene glycol and propanediol, respectively) could be regularly confused for each other. The two ingredients are very similar and even share the same chemical formula; however, they have different chemical structures (as cosmetic chemist Michelle Wong explains it, the alcohol group is connected differently), which changes the way they function.
But structurally isn't the only way the ingredients differ. Palep adds that propanediol is derived from corn, while propylene glycol is derived from petrochemicals. Although propylene glycol is determined to be safe in skincare and cosmetics, propanediol is commonly used as an alternative to propylene glycol for those who want products that don't contain petroleum-based glycols. Palep points out that not enough studies exist yet to determine if it's the safer option, but studies show propanediol is likely less sensitizing and irritating to the skin.
Side Effects of Propanediol
Generally, propanediol is safe to use in skincare products for those who do not have an allergy to it. Palep says although there could be a small risk of irritation for some, there are no serious side effects. In addition to irritation on the skin, propanediol can also irritate the eyes, so be sure to wash your hands before you touch your eye area.
How to Use It
Because propanediol has many different uses and is included in a wide variety of formulas, how it should be applied largely depends on the specific product, so use as directed by your dermatologist. Propanediol is safe to incorporate into your skincare routine on a daily basis. "In general, it can be used by all skin types," says Garshick. "For those with sensitive skin, it is always important to apply to a small area to ensure no reaction."
