Edited byRaja K. Sivamani, MD, assistant professor of clinical dermatology, University of California, Davis, USAJared R. Jagdeo, MD, MS, Department of Dermatology, University of California-Davis School of Medicine, Sacramento, California; and Department of Dermatology, State University of New York Downstate Medical Center, Brooklyn, New York, USAPeter Elsner, MD, Department of Dermatology, Friedrich-Schiller-Universität, Jena, GermanyHoward I. Maibach, MD, University of California School of Medicine, Department of Dermatology, San Francisco, USA