What is Keratin?

Overview
Keratin is the hair’s raw material: it corresponds to 95% of its final structure, and its characteristics are genetically transmitted. People often wonder whether it is a living body. It is difficult to say so: its multiple properties mean it is a complex substance, difficult to classify.

Contents
Composition
Formation and Keratinisation
Properties
Keratin and Heredity

Composition

Keratin is a highly resistant fibre protein, made of long chains of amino acids, aligned with the hair’s vital axis and made of multiple layers of twisted fibrilla.

Those protein chains are kept together by the sulphur molecules, thus building laterally laid bridge-like connections (disulphur bridges). They bring to the chains their stiffness and adhesion. All of this forms the sulphured amino acids.

In the construction of keratin, there are three such specific acids: cystine, methionine and cysteine. They are channeled by the blood until the hair root and require an intake of zinc and vitamin B6 in order to be synthesised. You will find those elements in all the dietary complements aimed to reinforce the hair’s strength.

Worth noting: keratin is the common constitutive of all the phaners: this word means ‘apparent’ in Greek and designates all of the skin’s external productions: nails, claws, horns, beaks, hoofs, etc.

Aligned twisted fibrilla linked by disulphured bridges

Formation and Keratinisation

Keratin is produced by keratinocytes, which are the hair’s mother cells fed by the papilla’s blood. Located in the matrix, at the deeper level of the hair follicle, the cells become divided into daughter cells, during the whole anagen phase of a hair’s life cycle.

The keratinocytes never stop their action, in a perfectly synchronized and merciless motion… As soon as they are formed, the daughter cells double themselves, remove the previous ones and make them die by pushing them away towards the top. They then die, in turn, in order to leave room for the new ones.

Keratin is born from this stocking of dead hardening cells (keratinisation) and constantly move up the hair follicle in order to form, in surface, the hair as we see it.

The matrix’s cells moving upwards

Properties

1

Permeability

Keratin is sensitive to humidity, just like a sponge, and can retain up to 40% of its weight in water. The hair then starts to swell and can gain 15 to 20% in diameter. The surrounding humidity thus considerably modifies the hair’s physical structure.

Coloration. This hydrophile power is largely used in cosmetics in order to change the hair’s colour. Under the action of alkaline liquid, the cuticle’s scales are raised, like dish tops, in order to let the colouring product pass into the cortex and modify the hair’s natural pigmentation.

If the process is not carried out properly, or is too frequent, the scales do not close themselves properly, and the hair becomes split and porous. In extreme cases, the keratin becomes so porous that the hair can no longer be coloured.

Cuticle

2	Elasticity Elasticity is the keratin’s most amazing property. In the cortex, the fibres, twisted in a propeller-like way, enable the hairs to extend themselves like a spring, and then to easily regain their initial length. Those fibres act like a real shock-absorber and you can test it for yourself by taking a hair, and slightly stretching it: it will become 20 to 30% longer, without breaking. When you will release it, it will regain its initial shape. Now, take a wet hair, and try again: it can stretch up to 50%. If your hairs do not pass those tests, if they break, that means they are not in good health.
3	Resistance Its diameter does not exceed one tenth of a millimetre, but in order to break a hair’s keratin, the weight needed varies from 50g (African type hair) to 100g (Asian type hair). A head of 100,000 hair could thus support from 500 to 1,000 kg. But this remains very theoretical, as the scalp would in fact break off before reaching that weight!
4	Durability Keratin is not sensitive to disintegration, and it preserves the traces of all the substances provided by the blood to the keranocytes during its production. In the hair of sportsmen, we are thus able to trace doping products longer back in time than via blood or urine. The keratin’s imputrescibility is also used to make the dead speak. The best known example is Napoleon’s: because arsenic was found in his hair, historians concluded that his English guards had poisoned him. Another famous example, from the 1950s, is the case around Marie Besnard, called the poisoner, with strong disagreements among experts around the analysis of her 11 alleged victim’s hair . The debate led to 3 trials and lasted 10 years.
5	Natural colour Produced in the hair’s matrix, the melanocytes are the cells that synthesise the melanine pigment and transmit it to the keranocytes in order to colour the keratin. They disappear with age, which causes the hair to whiten. There are two types of pigments present in the keratin: the granulous ones, brown or black, that regulate the dark or ‘redish’ colour tones, and the diffuse pigments, from yellow to brown, that regulate the blond tones. It is the mixture of the two types that determines the hair’s natural colour, and explains the infinite range of colours found. That is why we say that, as for fingerprints, there are not two identical hair colours. In France, over 50% of the population has brown hair. For over a century, with the influx of immigrated population, that percentage has kept going up. The smallest group is red hair, which corresponds to only 5% of the population.

6	Plasticity A susbtance’s plasticity is its ability to preserve a given shape. Keratin is well adapted for this: with heat and water, brushing the hair temporarily changes its shape. The hair’s plasticity also enables a long lasting change of its natural shape. It is a common cosmetic procedure: all that is needed is to break the disulphured bridges, which are the keratin’s vulnerable points (its Achille’s heal) with a chemical agent. The fibres then lose their structure and stiffness, and become ‘invertebrates’. Once the desired deformation is obtained, the bridges are joined back by oxidation, and the keratin regains its consistence. That is how straightening and perms function. The procedure is far from being harmless. If the chemical products are too aggressive, or if the necessary pauses are not applied, the fibres do not restructure themselves properly, which leads the hair to start scaling, thus becoming easily breakable.
7	Electricity Keratin is an isolating material that easily traps static electricity. The hair will become all the more electrically charged if it lacks sebum, if its cuticle is damaged, and if the outside air is dry. There are different ways to diminish the effects of such an inconvenience. See Electrically charged hair
8	Shine It is the hair’s ability to reflect light. On a healthy keratin, the cuticle’s scales, which are well stuck together by their ceramids, show a perfectly smooth and flat surface that enables reflection. Inversely, if the scales are open and irregular, the surface’s roughness makes the hair dull.
9	Sensitiviness The keratin’s quality is sensitive to three factors: Sexual hormones, especially androgen, that govern its growth. Stress, that can modify its diameter, resistance, colour and life length. The diet, that must bring, daily, the ingredients needed for its development: sulphured proteins (mainly found in meat and fish), zin, iron, vitamins A and B, essential fatty acids, and vitamin E. People at risk Vegetarians, whose keratin is thinning, must monitor very closely their RDA in protein and iron. In that case, the daily diet should be supplemented by complementary nutrients (such as brewer’s yeast, for protein, and spirulina, for iron). It is the same thing for women who lack in iron: their hair’s keratin can dangerously thin out. It is then necessary to compensate with nutrients that are particularly rich in iron, or with spirulina, or auxiliary medical drugs.

10

Fragility

This property is not incompatible with the previous ones, as keratin, at the hair stem level, is a dead substance… Of course, it is attached to the rest of the system via the hair root, but, as soon as it is produced by the keranocytes, it no longer receives any support.

The cuticle is thus sensitive to the mechanical deteriorations caused by bad treatments. When it is excessively aggressed, it can even disappear, thus leaving the cortex naked and defenseless. See What is an Aging Hair?

If the keratin is damaged, the barrier constituted by its cuticle’s ceramids should be rebuilt by an intake of vegetable oils rich in essential fatty acids and vitamin E (aloes, soft almond, avocado, borage, rape, soy, cotton seeds, shea, corn, macabia nuts, olive…) See Clauderer Boutique Creams and Baulms

Very scaled cuticle under an electronic microscope

Keratin et Heredity

Quality. The keratin’s characteristics are genetically transmitted. It can thus be more or less thick or coloured, stiff or supple, according to each person’s genome, that is their family and ethnic heredity.

Thinning. Throughout one’s life, keratin can considerably weaken compared to how it was at birth. The most common reason for alteration is caused by the androgenetic factor. If no treatment is started, the progressive thinning becomes irremediable. This factor is also genetically transmitted, although the damages that it causes never appear before puberty.

Whitening. The moment when keratin only produces colourless hair, because its melanine production has stopped, is also genetically determined.