Propylene glycol is used in moisturizing creams as a humectant. Humectants help in the retention of moisture. Due to its composition Propylene Glycol penetrates the skin (more so than other humectants) and takes along with it any toxins that may be present in the product you're using or the environment. This may cause skin irritations.
It can also cause allergic reactions for those with eczema and other skin allergies even when used at the concentrations recommended as safe by the Cosmetic Ingredient Review.
And though it's recommended that our exposure be limited to small amounts on an infrequent basis this is impossible to do as propylene glycol is in almost all personal care products even those considered "high-end."
So what's the solution? I use a natural alternative in my products-glycerine, a plant based humectant that's safe and gentle on skin.
How simple is that?