Abstract : Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease in which epidermal barrier dysfunction and immune dysregulation are closely interconnected. In recent years, clinical guidelines and mechanistic studies have increasingly emphasized that impairment of the skin barrier is not merely a secondary phenomenon but a central driver of disease persistence and relapse. Consequently, emollient-based skincare is now regarded as a fundamental component of therapy rather than a cosmetic adjunct. Filaggrin plays a pivotal role in epidermal barrier integrity. Its deficiency-resulting from loss-of-function variants in the FLG gene or secondary suppression driven by type 2 inflammation-leads to reduced levels of natural moisturizing factor (NMF), increased transepidermal water loss (TEWL), altered stratum corneum pH, lipid-processing disturbances, and enhanced penetration of irritants, allergens, and microorganisms. These changes contribute to a self-amplifying cycle in which inflammation further impairs barrier function, thereby sustaining disease activity. This narrative review summarizes current evidence (primarily from 2023–2025) on epidermal barrier dysfunction in AD, with particular emphasis on the role of filaggrin and its clinical consequences. In addition, it discusses the practical relevance of emollient-based skincare across different disease phases and patient phenotypes, highlighting adherence and patient education as key determinants of long-term treatment success.