There are three main types of ingredients found in moisturizers: occlusives, emollients, and humectants. Emollients contain a mixture of oil and water and work to help soften and smooth the skin. Occlusives (such as petrolatum) work by forming a protective layer that locks in moisture and helps prevent water from evaporating off your skin. Humectants (such as hyaluronic acid) attract and hold moisture in your skin. CeraVe's hydrating moisturizers feature these barrier-supporting ingredients—in addition to our three essential ceramides—that help maintain your skin’s protective barrier. This protective barrier is essential for skin health, as it keeps much-needed moisture in and external irritants out. Learn more about the science of ceramides in The Ceramides Difference.