Eczema, or atopic dermatitis (AD), is a chronic inflammatory skin condition affecting approximately 200 million people worldwide, with its incidence rising significantly in recent decades, particularly in high-income countries. It typically begins in the first year of life but can manifest at any age. Eczema often follows a relapsing–remitting course, requiring ongoing treatment to manage symptoms. While many children with eczema experience improvement or resolution by late childhood, a substantial proportion continue to be affected into adulthood, with flare-ups occurring even after long periods of remission. The aim of this review is to provide a comprehensive examination of eczema (atopic dermatitis) across the lifespan, with a particular focus on its epidemiology, pathophysiology, and impact on different age groups, including children, adults, and the growing population of older adults. This review seeks to explore the current understanding of the disease's progression, the diverse life-course trajectories of eczema, and the implications of these trajectories for treatment and management. Additionally, the review aims to highlight the gaps in existing research and identify future directions for improving the prevention, management, and quality of life for individuals affected by eczema at various stages of life.