Effect of Moisturizers on Epidermal Barrier Function

The skin barrier is a critical structure that preserves continuous skin homeostasis by protecting the body from external environmental factors and regulating transepidermal water loss. The functional integrity of the skin barrier primarily depends on the structural organization of the stratum corneum and the composition of intercellular lipids. Disruption of this structure can result in various skin problems, including dryness, increased sensitivity, and inflammatory reactions. Recent studies demonstrate that skin barrier impairment constitutes a shared pathophysiological mechanism underlying various dermatological conditions, including skin aging and atopic dermatitis. This review presents an integrated overview of the skin barrier outlines the major mechanisms involved in its disruption. Emphasis is placed on the roles of corneocytes and intercellular lipids within the stratum corneum. Skin barrier dysfunction is examined in the contexts of xerosis, aged skin, and atopic dermatitis. In addition, the mechanisms of action of moisturizers are systematically reviewed based on their classification as humectants, occlusives, and emollients, emphasizing their contributions in maintaining skin hydration and promoting barrier recovery. Furthermore, recent research trends on physiological lipid-based moisturizers containing ceramides, cholesterol, and fatty acids are explored, with particular attention to their potential applications in barrier-compromised skin conditions. This review aims to offer a cohesive scientific perspective on barrier-oriented moisturization strategies, thereby providing a theoretical framework for the development of skin barrier-focused cosmetic, cosmeceutical, and clinical skin care approaches.