The stratum corneum, or the outermost layer of skin, is made up of dead skin cells kept together by a natural oil called sebum. This layer works as a barrier to prevent moisture loss from the skin when it is intact and healthy. As the skin gets dry, however, this barrier is compromised, and moisture evaporates from the skin faster. For this reason, it's important to choose skincare products that are formulated to be gentle and hydrating. Products with hyaluronic acid, ceramides, glycerin, aloe vera, and vitamin E are the right ones to keep your skin always healthy and with appropriate levels of hydration.