1. Introduction

Scalp hair is a defining element of our physical appearance with significant psychological and social impacts in our daily life. Everyone within any society has an abstract, unique and innate idea of beauty. As hair is one of the physical features which is easier to modify in terms of length, color or shape, the pursuit of the desired and idealized hairstyle to achieve beauty drives many consumers and feeds a vast global cosmetic industry.

Each individual is unique regarding hair growth rate, size and shape, but there are general properties of the hair fiber that can be grouped according to the ethnic background. The cosmetic industry considers three primary geo-racial hair types—African, Asian and Caucasian—with distinct hair fiber shape characteristics (diameter, ellipticity, and curvature) that control much of the cosmetic and physical behavior of human hair.

3,4,5,6,7,8,9,10, The physicochemical properties and shape of the hair is the direct result of the organization of its various structural elements, proteins being the most significant. Hair shape is defined in the hair follicle: large hair follicles produce “terminal” hairs (scalp), small follicles produce fine “vellus” hairs (body hair), curved follicles produce curly hair in all ethnicities [ 1 2 ]. Particular hair fiber shapes can be associated with polymorphisms/mutations in certain genes; furthermore, some proteins were shown to be expressed asymmetrically in a curly hair follicle bulb [ 2 11 ].

While hair styling is an ancient practice, permanent wave or hair straightening treatments only appeared as a commercially available and reliable service for the intentional control of hair shape in the 19th and early 20th centuries, respectively. The available methods for hair straightening/waving rely on the rearrangement of intermolecular bonds, based on cosmetic emulsions of high pH and reducing power. These hair procedures can have very negative consequences for hair, scalp and even consumer’s health. When hair is systematically exposed to permanent chemical treatments, it becomes, sooner or later, damaged. This damage can affect only the hair fiber surface attributes like smoothness, porosity and shine or it can affect the fiber core texture (thickness), and mechanical properties. Because the hair fiber is a non-living structure, its damage caused by cosmetic or environmental factors is irreversible. It is critical to have appropriate hair care procedures to improve function and prevent further damage, as hair fibers cannot be restored to their original structure. If the hair follicles are not affected, the subject has to wait for hair fibers to grow, which can take a long time, depending on their size and growth rate.

The consumer awareness of these problems is the driving force and the source of many potentially major changes occurring in the market, which creates a new niche for alternatives to traditional hair procedures. The future of cosmetic science will be the development of more powerful hair care treatments for damaged hair and of new cosmetics that allow the safe and specific control of hair morphology.