These natural compounds last a shorter time than most chemical preservatives, but they adequately preserve herbal skin care products and give you the benefit of their own nourishing qualities. Propylene Glycol (PG) & Butylenes Glycol are petroleum plastics widely used in car anti-freeze and skin care, despite the fact that they can penetrate your skin and weaken protein and cell structures. PG is so strong it dissolves stainless steel in 48 hours and can only be kept in plastic containers. The EPA insists it only be handled wearing protective gloves, clothing and goggles. But some skin care manufacturers use concentrations of up to 20 percent of it. I could make a very long list of widely used, dangerous chemicals, but I think you can see that there is a trend here. It's this. The big chemical companies don't mind putting dangerous toxic chemicals into your skin care products. And the reason is obvious -- these are thick-skinned businesses (no pun intended) that exist simply to return profits to shareholders. Synthetic chemicals are cheaper than herbal ingredients.