Hair

Hair is a keratinized fiber that emerges from the skin surface. Hair fiber have many qualitative characteristics such as it may be thick or thin, straight or curly, long or short. This material has been taken care of since the earliest stages of evolution (grooming). The activity has been organized into professions (hairdresser salons, hair removal institutes, etc.). After the era of industrial revolution, hair, initially the exclusive battlefield of cosmetic companies, has now become a focus of great interest to the medical community. New research and measurement technologies are being developed on a day-to-day basis as the scientific community has invested a lot of effort in the recent years (1). In this chapter we shall provide the reader with some basic numbers and statements. At this stage of the reading, we stress the fact that we consider skin and hair so intimately interacting that they are part of a system. Any compound that is supposedly applied only on the hair may sooner or later come into contact with the skin. At first glance, this may seem trivial but an often-neglected dimension! Who would ever think that a shampoo or a hair dye might induce an allergic reaction that in turn results in hair shedding? As safety is addressed in other sections of this manual, let us focus on the fiber and its life cycle.