Skin moisturisation is the process of maintaining optimal hydration levels within the stratum corneum, the outermost layer of the epidermis. This is crucial for preserving the skin's barrier function, preventing transepidermal water loss (TEWL), and protecting against environmental aggressors. Adequate moisturisation supports skin elasticity, softness, and overall health, mitigating conditions like xerosis and dermatitis. It involves both intrinsic factors (e.g., natural moisturizing factors, sebum) and extrinsic applications (emollients, humectants, occlusives).