Propendiol

CAS No- 504-63-2

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, Palep describes propanediol as a natural alternative to propylene glycol. It can be found in cosmetics and personal care products, like 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.2Dissolves 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.3
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’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 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.2