The longitudinal course of atopic dermatitis (AD) is heterogeneous and complex. While previously thought to be a childhood disorder, recent studies demonstrated that childhood-onset AD may take several different courses that may involve persistence into adulthood becoming a lifelong condition. Other patients only demonstrated adult-onset AD. Different factors may play a role in the timing of AD onset. Assessing the longitudinal course also involves understanding the changing temporal pattern of AD. Understanding the dynamic course of AD is important in identifying individualized treatment recommendations for patients.