Our skin is comprised of two main layers the dermis and the epidermis and has many functions such as acting as a barrier to the outside world. It helps regulate temperature, keeps germs and irritants out and helps keep moisture in. Within the epidermis there are five layers. The outer most layer called the stratum corneum is comprised of cells and fat-like materials called lipids. Elias described this layer as bricks and mortar: the bricks being the cells and the mortar being the lipids. The intercellular lipids are comprised of 40% ceramides, 25% cholesterol, 25% free fatty acids and 10% cholesteryl sulfate. Ceramides have been found to be the most important component in the stratum corneum for maintaining barrier function.
Up to nine different ceramides have been identified in the skin and within the ceramides there are two types: Sphingosine and Phytosphingosine. It is the type of ceramide and its structure that determines the function of the ceramides, but their overall function is to help maintain the water retention in the stratum corneum. Many things can deplete skin of its moisture such as detergents or harsh weather. This can rob the skin of lipids needed to help maintain a healthy barrier. A damaged or depleted barrier can lead to irritation, increased skin sensitivity and skin dryness.
Humectants such as glycerin (a common ingredient in skin moisturizers) are valuable for providing immediate relief from dryness, but they only provide short-term relief of dry skin. Long term relief from dryness needs to come by replacing what is naturally found in the skin. As ceramides are the main component of the intercellular lipids and contributing to water retention to the skin they become crucial to providing long term relief of dryness and decreased skin sensitivity. Ceramides can be incorporated in skincare products for their moisturizing properties.
Kao has led the research in synthesizing molecules that retain moisture. They have developed an ingredient called SPLE that works similar to the ceramides found naturally in your skin. Kao has been able to prove through research that their SPLE provides the moisture retaining benefits of a natural ceramide. While natural ceramides can be used, Kao's ceramide has been optimized and the structure allows for increased moisture binding properties of the skin.