Atopic eczema (synonymous with atopic dermatitis) is a common heterogeneous phenotype with a wide spectrum of severity, from mild transient disease to a severe chronic disorder with atopic and non-atopic comorbidities. Eczema is a complex trait, resulting from the interaction of multiple genetic and environmental factors. The skin, as an organ that can be biopsied easily, provides opportunities for detailed molecular genetic analysis. Strategies applied to the investigation of atopic eczema include candidate gene and genome-wide studies, extreme phenotypes, and comparative analysis of inflammatory skin diseases. Genetic studies have identified a central role for skin barrier impairment in eczema predisposition and perpetuation; this has brought about a paradigm shift in understanding atopic disease, but specific molecular targets to improve skin barrier function remain elusive. The role of Th2-mediated immune dysfunction is also central to atopic inflammation, and has proved to be a powerful target for biological therapy in atopic eczema. Advances in understanding eczema pathogenesis have provided opportunities for patient stratification, primary prevention, and therapy development, but there remain considerable challenges in the application of this knowledge to optimize benefit for patients with atopic eczema in the era of personalized medicine. Copyright (C) 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.