1 Chapter 1 The Structure and Chemistry of Human Hair J. Alan Swift Swift Hair Consultancy Introduction In this chapter, much derives from the use of the transmission electron microscope for examining the internal structure of human hair. Most components of the fiber are described in detail and their chemical, mainly protein, compositions are highlighted. Particular attention is paid to the internal structural organization of the keratin intermediate filaments. “As a species we exhibit an overwhelming preoccupation with our hair and, more sadly in our later years, with the lack of it.” This opening line of the book on hair by Wendy Cooper1 embraces many of the preoccupations of our present book a book within which knowledge of the structure and chemistry of human hair is of key concern. Human hair, like all mammalian keratin fibers, is a remarkably resilient biological material and has often been recovered from ancient sites for scientific study. Such is the hair, amongst many others, from ancient Egyptian mummies2, from Iron Age people buried in the bogs of Denmark3 and, perhaps of more recent fame, from the so-called Ötzi iceman found in a glacier at the head of the Austrian Ötztal valley, near the Italian border.4 There is little doubt in all these cases that the hair has survived because it was protected from the damaging effects of sunlight. In this regard, exposure to