Robert Baran, MD, is formerly Head of the Nail Disease Centre and of the Dermatology Unit, Cannes General Hospital, and Honorary Professor of the University of Franche-Comté, France. He is also the editor of Baran and Dawber's Diseases of the Nails and Their Management 5E, Fungal Infections of the Nail and Scalp 3E, and Nail Therapies 2E, amongst many others. Howard I. Maibach, MD, is Professor of Dermatology at the University of California School of Medicine, San Francisco, California, USA. He is also the editor of Dermatotoxicology 8E, Handbook of Cosmetic Science and Technology 4E, and Handbook of Systemic Drug Treatment in Dermatology 3E, amongst many others.