This is an ingredient widely used in cosmetics as a penetration enhancer. It's considered "natural." Please tell me where this ingredient is naturally occuring in nature. Here is the definition of Propylene Glycol from the web. "Propylene glycol (also known as 1,2 propanediol) is a relatively small molecule with two alcohol (hydroxyl) groups (-OH). It is a colorless, odorless liquid that is completely water-soluble. PG is a synthetic product obtained from the hydration of propylene oxide, which is derived from petroleum products."
Here is why it's used. "In the skin and hair, propylene glycol works as a humescent, which causes retention of moisture content of skin or cosmetic products by preventing the escape of moisture or water. Propylene glycol is one of the most widely used cosmetic ingredients, as it is a humectant. It is a clear, colorelss, viscous liquid, slightly bitter-tasting. Propylene Glycol USP is the most common moisture-carrying vehicle, other than water itself, in cosmetics. Absorbs moisture, acts as a solvent and a wetting ingredient." It's also tested in a lab on animals.
We use local, slightly filtered beeswax (which IS natural) instead of this ingredient.