Oils are not water soluble, which means that they trap water and other goodies in your skin when used. However, if an oil is applied at the wrong time in your skin care routine, it can also keep the amazing products you are using out. For example, our Face Serum is water soluble and is meant to penetrate deeply into your skin, but if you were to use an oil before applying your serum, that water based serum would not make it past that layer of oil and never be able to reach your skin. This is why you would want to use it as a final step after a moisturizer, like our Daily Moisturizer.