To learn to solve the various different problems that can affect our hair, we need to know exactly what a hair is, what elements it is made of, how it originates, how it dies, and how it is cyclically regenerated.

Hair grows within a diagonal hair follicle in the outer layer of the skin. The hair follicle is therefore the point at which the hair shaft (the visible part of the hair) forms. At the base of the hair follicle is the bulb where the hair grows and new hair cells are formed. The hair bulb surrounds a bundle of blood vessels which is surrounded by a special connective tissue called papilla. The bulb contains the only living cells; all the rest, including the hair shaft, is made up of dead cells. Keratin, the material hair is made of, is a very strong, fibrous protein: hair can in fact last thousands of years without decaying if it is not contaminated by chemical agents. In the upper part of the hair follicle is a sebaceous gland, which secretes sebum and thereby determines the type of hair – oily, normal or dry. IF WE EXAMINE THE HAIR AND CUT IT IN CROSS SECTION, WE MAY IDENTIFY THREE PARTS: 1. Medulla. The central part of the hair shaft, formed of cells with no nucleus, arranged in a row. 2. Cortex. Formed of elongated cells containing the melanin components that determine the colour of the hair and form its most voluminous part. 3. Cuticle. A thin membrane formed of horny cells shaped like overlapping scales which constitute the part of the hair we can see. The cuticle is very important aesthetically: if it is in good shape the hair will look beautifully glossy and fluffy. THE GROWTH CYCLE. Like many other natural processes, the growth of human hair is a cyclical mechanism. Healthy hair goes through three stages. The first of these, growth, takes two to six years and is characterised by continuous formation of new cells in the bulb. After this period the bulb’s function is completed; the hair goes into a transitional phase that lasts about two weeks, before entering a phase of rest which lasts two to four months. At the end of the third phase the hair falls out painlessly, making way for the new hair that is growing below it. A new growth phase begins. » Anagen (growth phase). The hair is perfectly healthy as it develops. » Catagen (involution phase). The hair is approaching the end of its life cycle. » Telogen (rest phase). The old hair is ready to be expelled. A new anagen phase begins, and the cycle continues. Chemical analysis of the hair reveals its principal constituents, other than water: keratin, lipids, minerals and pigments. KERATIN. Keratin is a protein contained primarily in the cortex (of which it is the principal component); there are 18 amino acids in keratin, but the ones that make up most of its substance are cysteine, cystine, serine, glutamic acid, glycine, threonine, arginine, valine, leucine and isoleucine. Polypeptide chains are made stable by three types of “bond”: hydrogenated bonds (which contribute solidity), bonds between acidic chains and basic chains (which are broken by strong acids) and disulphide bridges (which cause the hair to curl when they are broken, for instance in a “permanent wave”). Keratin can be shaped with steam (to style the hair). LIPIDS. Consisting of triglycerides, waxes, phospholipids, cholesterol, squalene and free fatty acids, most of which are sebum derivatives. MINERALS (TRACE ELEMENTS). Trace elements are an essential component of protein and enzyme systems. There is a direct correlation between the quantity of trace elements present in the blood and those present in the hair: a) iron: more abundant in red hair than in blonde or dark hair. b) magnesium: more abundant in black hair. c) zinc: essential for the proper activity of the cells that germinate the matrix. Without it, the hair weakens and grows more slowly. d) copper: essential in the process of synthesising melanin and permitting oxidation of cysteine to form cystine, with formation of disulphide bridges. e) lead: more abundant in brown hair. Insufficiency of protein and/or minerals can be seen when observing the hair through a microscope, as the hair shaft will be thin, with a very small bulb (though if the hair is normally thin, bulbs will appear normal). PIGMENTS. Represented by melanins, colourants present in hair in a diffuse or granular form. Insoluble in water, but soluble in strong acids, they can be stripped using hydrogen peroxide. Melanocytes synthesise two main types of melanin: eumelanin, which is dark, present in black hair, and lighter feomelanin, present in golden, blonde and red hair. Its structure gives the hair two important features: » Elasticity: if the shape of the hair is modified while drying, it will go back to its original state over time; » Strength: normal healthy hair can support a lot of weight before it breaks. A number of factors can make hair sensitive, causing deterioration of the structure of its keratin fibres. Many factors can alter the structure of the hair: environmental (the sun’s rays, seawater, swimming pool water, pollution), thermal (blow dryers, curling irons, straighteners), mechanical and chemical. These factors modify the chemical and physical properties of the hair; changes which take place in the bonds inside the cortex can make the hair extremely fragile, especially at the ends, which tend to split and break. The porosity of the hair shaft also increases; the hair then becomes frizzy and hard to comb, absorbs moisture and water and takes longer to dry. Finally, the surface of the hair shaft is modified: the cuticle is altered, appearing dull, dry and fragile. The hair has a very special structure, different from that of skin: it is not regenerated automatically and when subject to stress, it is weakened and becomes flaky. BUT WHAT HAPPENS deep down inside the hair? 1. The hair’s protective barrier (hydrolipidic film) is weakened. Due to both internal and external causes, this protective shield ceases to perform its barrier function. 2. The hair scales start lifting. Scales overlap like roof tiles, and are closely connected in healthy hair; when damaged, however, they open up and come off the hair. The result is that the water normally stored in the hair begins to evaporate and the hair dries out completely. 3. Keratin in the centre of the hair is destroyed. Damaged by the trauma, the keratin chains constituting the hair break. The hair becomes fragile and porous and breaks. Reconstruction becomes necessary to nourish and moisturise the hair right down to its core. Hair reconstruction is a beauty treatment that rejuvenates the hair fibre and restores the layers of keratin that have deteriorated with time. Anyone who wants to take good care of their hair should periodically undergo a hair reconstruction treatment to help keep the hair looking young and healthy, from the roots to the tips! And to close, a few fun facts about hair: » Men’s hair grows faster than women’s » Hair grows faster in warm weather » Hair grows more slowly with age » Cutting hair and shaving does not affect the speed at which hair grows » Men’s hair is thicker than women’s » The density of the hair decreases with age