We continue to choose to formulate with plant- and naturally-derived ingredients. The Propylene Glycol that we use in our washes is sourced from vegetable glycerin and has antimicrobial properties. It also functions as a humectant that can support the moisture profile of a product. You can read more about the Propylene Glycol that we use in our washes here: What is Propyolene Gylcol? Tell me more.