The Krutmann working group investigates the molecular mechanisms that underlie environmentally-induced skin aging and associated skin diseases. Major discoveries include: (1) the observation that the AHR is critically involved in the UVB stress response; (2) a potentially curative therapeutic approach for the UV-sensitive progeroid Cockayne syndrome; (3) the identification of traffic-related air pollution as a causative factor for skin aging/pigmentation; (4) the identification of near infrared rays as causative for skin wrinkle formation; (5) the definition and characterization of the skin aging exposome; (6) together with Klaus Unfried the development of an ectoine-based medical product for the protection against particle-induced lunge diseases; (7) the identification of two cutotypes in the skin microbiome of Han Chinese. J. Krutmann has regularly coordinated structured research consortia such as RTG 1033, SFB 728 and LRA Healthy Ageing.