The outermost layer of skin, known as the stratum corneum, is vital for both keeping the body properly hydrated and shielding it from outside threats. The stratum corneum lipids, which form a complex matrix that aids in controlling water loss and provides protection from infections, are essential to its functions. Ceramides, cholesterol, and free fatty acids make up the majority of these lipids, and each one specifically contributes to the skin's barrier qualities. Ceramides are sphingolipids with a special structure that allows them to organize into lamellar structures. Ceramides make up around 40–50% of all the lipids in the stratum corneum. By forming a hydrophobic barrier, these structures stop the skin from losing water. Ceramides are involved in cell signaling as well, which affects things like cell differentiation and proliferation.About 25% of the lipids in the stratum corneum are cholesterol. It is essential for preserving the lipid bilayers' stability and fluidity. In order to keep the lipid barrier intact and prevent excessive crystallization, cholesterol molecules intersperse between the ceramides and fatty acids. The skin's ability to operate as a barrier against irritations and increased water loss can be jeopardized by insufficient cholesterol. Free fatty acids, which make up 10–15% of the lipids in the stratum corneum, help the skin's barrier function even more. They contain antibacterial qualities that aid in preventing skin infections. They are produced when triglycerides in sebum hydrolyze. Similar to ceramides, free fatty acids support the lipid matrix's lamellar architecture, which improves its capacity to stop water loss and keep the body hydrated.These lipids are dynamic; variables including age, environment, and skin type can affect how they are composed. Skin conditions like xerosis and atopic dermatitis can be brought on by imbalances in these lipids. (dry skin). It is crucial to comprehend the function of stratum corneum lipids in order to create skincare solutions that effectively maintain the skin's natural barrier function. Skincare formulations can help to increase skin moisture, protect against external stressors, and promote general skin health by replacing and maintaining these lipids.
