Chemical Properties of Hair & Hair Damage by Chemicals
What does hair actually consist of?
From a chemical point of view, hair belongs to the group of proteins (proteins). They make up the main component (65-95%) of the weight of the hair – they are macromolecular substances that contain hundreds of thousands of molecules. Proteins can be further divided into smaller parts, so-called peptides. Each such peptide then consists of even smaller elements - amino acids. There are around 21 types of them present in the hair.
About half of the hair proteins have a globular, disordered structure, the rest have an ordered helix-like structure called an alpha-helix.
The basic hair protein is keratin, and the basic amino acids in hair are cystin (an unstable substance that oxidizes easily) and cysteine. From 2 molecules of cysteine, 1 molecule of cystine is formed. They are connected to each other by strong sulfur disulfide bonds, which are resistant to external influences.
In addition to a large amount of protein, hair also contains water (12%), fat (3%), trace elements, carbon >, hydrogen, oxygen, nitrogen, iron, copper, zinc and iodine.
Amino acid molecules connect to each other in 2 ways:
- Using a CONH peptide bond
- Using a sulfur bond -S-S-
They bind the chains of keratin fibers together.
Chemical bonds in hair
There are 3 types of chemical bonds in keratin that determine the properties of the hair.
- HYDROGEN BOND
They are the weakest and can be easily disturbed by the action of water or weak bases. Disruption of hydrogen bonds occurs during hair washing, when the hair receives water, its volume and length increase by up to 30% and the scales = cuticles open. In this way, the hair can absorb the active substances contained in shampoos, masks and wraps. Stretched keratin is easier to shape. The bonds are rejoined after the hair has dried.
- SALT-IONIC BOND
They can be disturbed by the action of a solution of ammonia salt. In hairdressing practice, these bonds are disrupted during dyeing, bleaching and chemical preparation (straight hair becomes curly). The bonds break down due to the effect of high pH, allowing water and chemicals to penetrate deeper into the hair structure.
In this phase, keratin becomes soft, it is sensitive to mechanical influences (i.e. combing, rubbing, etc.) and the hair can be damaged very easily and quickly.
To explain it: By applying a bleaching or color mixture, the action of water and pH opens up the hair, first the hydrogen bonds are destroyed, then the salt bonds. The coloring or bleaching mixture penetrates to the cortex of the hair, where the melanocytes and the hair dye are present.
Cell membranes are dissolved and melanin grains are released - they are transformed into a soluble form. The effect of the alkaline environment (high pH) results in the oxidation of dissolved melanin. Hydrogen peroxide breaks down and releases active oxygen molecules. This active oxygen bleaches the hair melanin and the hair becomes lighter. During dyeing, a color emulsion also acts, which binds the resulting color after bleaching and attaches it to the melanin grains.
- SULFUR-DISULPHIDE
These are very strong and resistant bonds, both against water and against salt solutions and weak bases. In the hair, they are responsible for its strength. They can be disturbed only by the action of strong bases with reducing agents, most often solutions of salt and ammonia with salts of thioglycolic acid.
At the same time, keratin is transformed into a malleable, plastic form and we can shape it in various ways, but there is a risk of major damage to the hair, up to depilation - breaking the hair along its length (the hair loses its strength and falls apart).
Sulfuric bonds are also broken down during chemical preparation, i.e. if we want to make straight hair curly or vice versa. During these processes, the pH is incredibly high, which has a very bad effect not only on the hair, but on the scalp as a whole.
After bleaching and highlighting the hair, it is the most dangerous for the hair. In addition to hair and skin damage, improper handling or use could result inscalp burns or could hair start to fall out en masse after washing.
Unfortunately, this can also happen during bleaching. This happens less often with dyeing, but if the person is allergic to substances or has extremely sensitive skin, slight burns, swelling or hair removal may occur in this case as well.
Permanent hair damage by chemical actions
Whether it is dyeing, bleaching or changing the shape of the hair, each such intervention causes various and, above all, irreversible changes in the overall structure of the hair and its structure.
Cuticle damage manifests itself in loss of hair shine, split ends and if the hair is hit hard, it may even break. Hair tangles easily, is more porous and looks dry to rough. When the cuticle is damaged, an unprotected part of the cortex is exposed, which leads to a loss of moisture in the hair and to the breakdown of keratin fibers. This further causes the hair to weaken.
When working with chemicals, the hair is exposed to a lot of stress, which can lead to damage to the cortex in particular. Chemical preparation (transformation of straight hair into curly hair) and vice versa from curly to straight hair are among the strongest hair interventions. Their task is to permanently change the shape of the hair.
In order to achieve this change, the hair cortex must be exposed to strong chemicals. Due to the breakdown of sulfur -S-S- bonds and the formation of thiol -SH groups during preparation, there is increased friction in the hair and the hair becomes tangled easily. Not only during preparation, but also during hair bleaching, chemicals cause the breakdown of peptide chains, which leads to loss of hair mass and brittleness. The hair also loses a large amount of free amino acids, which play a decisive role in retaining moisture in the hair. With the loss of these amino acids, the hair loses its elasticity and becomes frizzy, dry and weak.
In a humid environment the hair absorbs more water and looks weighed down, tangled and with minimal volume. Because of this, it is more difficult to edit. Any further chemical intervention in the hair can cause its complete disintegration.
A one-time chemical treatment of the hair usually does not damage the hair follicle. It is precisely the long-term effect of chemicals on the scalp when the hair follicle can break, after which the hair falls out. A lot of hair loss/breakage immediately after the procedure happens with a serious chemical burn of the scalp, which occurs most often during hair preparation, bleaching, and in case of sensitive skin, during dyeing. The reason is:
- unprofessional handling of chemicals
- non-compliance with the time of action
- high concentration of chemicals
- allergy to chemicals
- hypersensitive skin
When working with these products, the hair is most stressed by the high pH. The pH of the skin is normally around 5.5 and the pH during chemical operations ranges from 9 - during preparation up to 11. A high pH causes softening of hair keratin and the breakdown of hydrogen, salt and partly sulfur bonds, making the hair vulnerable. When the effect of high pH is combined with strong concentrations of hydrogen peroxide during bleaching or with reducing agents during preparation, a strong disruption of keratin fibers can occur.
The complete disintegration of the hair structure occurs when the ordered structure of the alpha-helix cortex (also called the ortho-cortex) is changed by the effect of chemicals to the disordered structure of the para-cortex. The hair breaks down completely, becomes unmanageable, breaks and acquires the so-called "straw crepe effect".
Working with chemicals also damages the scalp. This is naturally protected by an acid/lipid coat, which forms an external barrier against moisture and envelops/protects the hair. The acid/lipid coating is the hair's primary protective system against external influences, UV radiation and insects, bacteria, fungi or dust.
This film thoroughly hydrates and softens the skin so that it is not dry, irritated and tense. It also helps retain moisture in the hair and its integrity. Damage to the protective coating with strong chemicals leads to loss of moisture, drying, and if we already suffer from some hair problems (e.g. dandruff or hair loss), this condition can be doubled.
This damage will (unless critical) heal itself. Our body produces an acid mantle naturally through the secretion of sebum and the production of sweat glands. Sebum production, however, decreases with age and the skin film requires a longer period of time to restore. To restore the acid mantle, it is recommended to use natural oils with a slightly acidic pH and substances that retain moisture in the skin.
Suitable compositiondiet, drinking regimen and vitamins mean a healthier body that will speed up the recovery of the missing shell and restore its function during the recovery process.
Whether it is dyeing, bleaching or changing the shape of the hair, each such intervention causes various and, above all, irreversible changes in the overall structure of the hair and its structure. I therefore appeal to avoid chemicals in hair care.