Issue link: https://www.ascpskindeepdigital.com/i/325995
Create your free business website! www.ascpskincare.com 23 THREE VITAL LIPIDS Under a microscope, the stratum corneum looks similar to a brick wall. The corneocytes are the "bricks," embedded in "mortar" that is made up of multiple sheets of lamellar membranes. These membranes are the permeability barrier, and they are made of a mixture of three different lipids: ceramides, cholesterol, and long-chain free fatty acids. These three lipids account for up to 10 percent of the dry weight of the stratum corneum, and they work together to waterproof the skin. The proportion of the lipids is vital for correct skin barrier function. All three must be present, and normal skin requires a ratio of 1:1:1 (in other words, each of the three is present in the same amount). If the epidermis overproduces or underproduces one of the lipids, a good permeability barrier cannot form. Skin problems are the result. An example is atopic dermatitis, a chronic inflammatory skin condition in which ceramides are not produced in sufficient quantities. Clients with atopic dermatitis need more ceramides, so a 3:1:1 ratio is used in products aimed at these clients. Although ceramides are a popular ingredient, the well-informed esthetician must realize that ceramides on their own are not the key to skin barrier repair, because all three key species of lipids within the permeability barrier are equally important. All three lipids must be present in sufficient amounts, and in the correct ratio, for the condition being treated. The Acid Mantle The stratum corneum's first line of barrier defense is the acid mantle on the surface of the skin. The acid mantle has many tasks. It contains trans-urocanic acid, our natural defense against ultraviolet (UV) radiation—this acid is responsible for filtering out around 70 percent of the UV-B rays that we are exposed to. Deeper within the skin, a key protein called filaggrin is metabolized (broken down) to provide essential barrier components. On the skin surface, these components are further degraded to produce what is known as "natural moisturizing factor," which plays a role in keeping the epidermis hydrated and overall barrier function. Maintaining the skin's surface at its natural, acidic pH level is critical for proper skin barrier function. When we strip away the acid mantle, the consequences include increased TEWL, chronic dry skin, various inflammatory conditions, and even an increased risk of skin cancer. What else happens when the acid mantle is removed? First, the skin's pH rises, making it alkaline instead of acidic. In response, the stratum corneum releases inflammatory cytokines in an attempt to trigger more lipid production. Normally, this would be a good thing and would help return the whole system to a healthy state. However, if this cytokine cascade is continual, chronic inflammation sets in. The result is a very thin, leaky, and permeable skin barrier. In other situations, increased skin pH may release serine proteases, which block lipid production. In this case, lipids stay trapped within the corneocytes instead of forming the permeability barrier. The result is complete failure of the skin barrier system. Although ceramides are a popular ingredient, the well-informed esthetician must realize that ceramides on their own are not the key to skin barrier repair.