From my point of view, penetration enhancers don't really contribute all that much to cosmetics. Considering that moisturizers and the like do most of their work on the surface layers of the skin, it doesn't seem all that useful. After all, some of the most effective moisturizers on the market are simple ointments with nothing more than glycerin and petrolatum. Most importantly, even if penetration enhancers made a slight difference, I highly doubt that consumers would be able to notice it. With that being said, I am still a university student and I don't have the extensive experience of others on this forum, so I'm interested in hearing from you guys.