Microbial dysbiosis and immune–barrier interactions in atopic dermatitis: a review

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease characterised by immune dysregulation, skin barrier dysfunction, and microbial imbalance, which collectively contribute to a substantial global health burden. Epidemiological evidence shows increasing prevalence worldwide, with pronounced rises in urbanised Asian populations and early childhood. Advances in molecular and multi-omics approaches have transformed skin microbiome research, revealing consistent patterns of reduced microbial diversity and dominance of Staphylococcus aureus, alongside complex interactions with protective commensals such as Staphylococcus epidermidis. These microbial shifts exacerbate type 2 immune responses and barrier disruption, establishing a self-perpetuating cycle of chronic inflammation. Advances in molecular and multi-omics approaches have enhanced understanding of AD heterogeneity, linking genetic factors, skin barrier impairment, and immune–microbiome interactions to disease pathogenesis. This review summarises current insights into the role of the microbiome in AD, emphasising host–microbe interactions, geographic and ethnic differences, and novel therapeutic opportunities targeting microbial modulation. Future progress requires harmonised, multicentre, longitudinal studies that integrate immunological, genetic, microbial, and barrier-related data to unravel AD complexity. Such approaches will enable precision medicine strategies and robust evaluation of novel interventions, addressing a critical need for effective and tailored therapies across diverse populations.