edited by Raja K. Sivamani, MD, MS, CAT, Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, USA; Jared R. Jagdeo, MD, MS, Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, USA, Department of Dermatology, State University of New York Downstate Medical Center, Brooklyn, New York, USA; Peter Elsner, MD, Department of Dermatology, Friedrich-Schiller-Universität Jena and University Hospital Jena, Jena, Germany, Howard I. Maibach, MD, Department of Dermatology, School of Medicine, University of California, San Francisco, San Francisco, California, USA.