soins capillaires décryptés
Plongez dans le monde des soins capillaires avec 'Haircare Decoded'. Nous savons que naviguer à travers la vaste gamme de produits et de traitements capillaires peut être écrasant. C'est pourquoi nous nous engageons à vous apporter des solutions efficaces et accessibles pour chaque besoin capillaire. Avec des formulations propres et hautement efficaces, la gamme JUST répond aux préoccupations capillaires courantes. Des ingrédients fortifiants aux traitements revitalisants, nous avons tout ce qu'il vous faut ! Mais comment déterminer votre type de cheveux ? Quels produits conviendront le mieux à vos besoins capillaires et fourniront les résultats que vous désirez ? Tout commence avec Hair Biology, et nous vous invitons à vous lancer dans ce voyage pour décoder tous ses secrets.
Structure des cheveux
Les cheveux sont présents sur presque toutes les surfaces de la peau humaine. C'est un fil de kératine fin avec une grande résistance et élasticité. Chaque cheveu se compose d'une racine ancrée dans le derme et d'un tige de cheveu qui dépasse de la surface de la peau. La racine est entourée d'une gaine tubulaire faite de cellules épithéliales appelée follicule pileux. La base de la racine et du follicule pileux est légèrement plus grande que le reste de la racine ; cette structure en forme d'oignon est appelée bulbe pileux.
Le bulbe pileux reçoit de l'oxygène et des nutriments via les vaisseaux sanguins qui alimentent les cellules en croissance active dans le follicule pileux autour du bulbe pileux, connu sous le nom de matrice capillaire.
Ces cellules sont la seule source de nouveaux cheveux. La tige du cheveu elle-même provient de la région bulbique de la racine et est produite par des kératinocytes de matrice se multipliant rapidement. La tige est entièrement composée de cellules mortes principalement constituées de kératine. Ces cellules restent attachées les unes aux autres par une substance intercellulaire semblable à du ciment.
Anatomie des cheveux
Si vous faites une coupe transversale d'un cheveu, vous trouverez trois composants majeurs, de l'extérieur vers l'intérieur : la cuticule, le cortex et la moelle.
Cuticule
Cortex
Medulla
The outermost structure is the cuticle. It is composed of multiple layers of keratinized, flattened cells, which overlap in a roof-tile. It is translucent, allowing light to penetrate the cortex pigments. It is composed primarily of keratin. The cuticle regulates the water content of the hair fiber, and is responsible for the luster and the texture of hair. The cuticle is the target for hair conditioning products. Shiny and soft hair reflects a healthy cuticle, while dry, brittle hair is the result of damaged cuticle cells.
Le cortex se trouve sous la cuticule et contribue aux propriétés mécaniques de la fibre capillaire, y compris la résistance, l'élasticité et la ondulation. Le cortex est constitué de cellules allongées riches en filaments de kératine ainsi que d'une matrice amorphe de protéines soufrées.
C'est la présence de mélanine dans le cortex qui donne la couleur aux cheveux. Avec l'âge, la quantité de pigment produite diminue, ce qui explique le grisonnement des cheveux. De plus, les changements liés à la coloration oxydative des cheveux, aux vagues permanentes et au lissage, ainsi qu'au coiffage thermique, se produisent tous dans le cortex. Le cortex, tout comme la cuticule, a une grande importance cosmétique, car ses propriétés optiques influencent fortement la couleur et la brillance de la fibre capillaire.
La moelle (le "cœur") est composée de cellules aplaties et kératinisées. Elle est considérée comme un cadre de kératine.
Cycle de croissance des cheveux et perte de cheveux
La croissance des cheveux est un processus unique et complexe qui implique des cycles continus de croissance et de régénération (phase anagène), de transition (phase catagène) et de repos (phase télogène). L'activité cyclique se poursuit tout au long de la vie, mais les phases du cycle changent avec l'âge.
Phase Anagène
Pendant la phase anagène, de nouveaux cheveux sont produits dans la partie inférieure du follicule pileux. Normalement, la plupart des cheveux du cuir chevelu (environ 85 à 90 %) sont en phase anagène à tout moment. Sur le cuir chevelu, la phase anagène peut durer de 2 à 6 ans, mais dans certains cas, elle peut être plus longue. Plus la phase anagène est longue, plus les cheveux peuvent pousser longtemps. La différence de longueur des cheveux chez les individus peut être liée à la durée variable de la phase anagène. Les cheveux du cuir chevelu poussent à un rythme normal d'environ 1 mm tous les 3 jours. Les cheveux sur les bras, les jambes, les cils et les sourcils ont une phase anagène beaucoup plus courte et un taux de croissance plus lent, ce qui explique pourquoi ils sont beaucoup plus courts que les cheveux du cuir chevelu.
Phase Catagène
La phase catagène est une brève phase de transition entre les phases de croissance et de repos, qui marque la fin de la phase de croissance. Sur le cuir chevelu, la phase catagène dure généralement entre 2 et 3 semaines.3 Pendant cette phase, la division cellulaire s'arrête, le tube folliculaire se rétrécit et se détache de la papille dermique, et la base du follicule se déplace vers le haut, vers la surface de la peau. La production de mélanine s'arrête durant cette phase, ce qui entraîne une extrémité inférieure non pigmentée des cheveux.
Phase télogène
La phase télogène est la phase finale et dure jusqu'à ce que le cheveu complètement développé tombe.\n\nLe cheveu tombe soit pendant la phase télogène, soit reste en place jusqu'à la prochaine phase anagène, lorsque le nouveau cheveu qui pousse\n\nl'éjecte. Sur le cuir chevelu, la phase télogène dure généralement environ\n\n2 à 3 mois. Dès que la phase télogène se termine, le cheveu revient à la première\n\nphase et tout le cycle recommence. Un nouveau cheveu apparaît du même follicule.\n\nL'élimination des cheveux télogènes est facile et indolore, ce sont les follicules pileux qui\n\nsortent lors du shampoing ou du coiffage des cheveux.
How you know whether you are losing the telogen or anagen hair?
The shape and color of the bulb are different for telogen and anagen hairs. Telogen bulbs are club shaped, and unlike anagen hair, their base is devoid of pigment. It can be clearly seen with a magnifying glass.
Other factors influencing hair growth are systemic factors, such as hormones, including androgens, estrogens, and thyroid hormones; growth factors and cytokines; as well as external factors linked to the environment, such as toxins, and deficiencies of nutrients, vitamins, and energy.
Chemical composition of hair
Hair fibers are primarily composed of various types of keratin. The keratin fibers consist of long molecular chains intertwined and firmly attached through various bonds. Bonds found in hair fibers are generally classified as strong bonds and weak bonds.
Strong bonds
Disulfide Bonds:
Hair keratin is made up of amino acids, where cysteine is one of the most important among them. Cysteine molecules with their sulfur atoms are able to form a very strong bond known as the disulfide bond. They contribute much to the shape, stability, and texture of the hair. When two cysteine molecules are bound together through a disulfide bond, a molecule called cystine is formed. Disulfide bonds are called strong bonds, because they cannot be broken up by heat or water, only chemically. These bonds remain intact when the hair is wet, allowing the hair to resume its original shape.
Weak bonds
Hydrogen Bonds (H-bonds):
H-bonds are relatively weak and can be easily broken by water and heat. They are primarily responsible for changing the hair’s overall shape. Although individual H-bonds are weak, they are present in the highest number of all types of bonds; therefore, they significantly contribute to the strength of hair fibers.
Salt Bonds:
Also known as ionic bonds, are sensitive to pH; therefore, they are easily broken by strong alkaline or acidic solutions. Although these are weak bonds, together they account for a significant part of the strength of hair fibers.
Van der Waals Forces:
These forces are weak attractive forces between neutral molecules in close contact. They can also be easily broken by water and heat.
Hair types
Based on Color
Natural color is the result of melanin present in the cortex. There are two types of melanin: eumelanin, which provides dark brown and black color to hair, and pheomelanin, which provides red to blond tones.
Naturalhair color ranges from black, brown, and blond to red with subtle hues in each category. The diversity of hair pigmentation results mostly from the quantity and ratio of eumelanin and pheomelanin.
Based on Condition
The hair’s condition refers to the smoothness and softness of the hair by touch, which is in direct relationship with the cuticle’s intactness. This is commonly called porosity, which reflects the hair fibers’ ability to absorb moisture.
- Healthy hair with a compact cuticle layer is naturally resistant to moisture.
- If the cuticle is damaged, hair has a course texture and loses its shine and smoothness. In such cases, the cuticle is raised, meaning that the layers are not tightly packed. This type of hair is referred to as porous or overporous hair if damaged severely. Porous hair can absorb liquids very easily and quickly and tends to develop split ends.
The hair fibers’ condition should be considered before undergoing chemical processes, such as hair coloring since the needs of damaged and healthy hair are different.
Based on Curliness
Refers to the shape of the hair shaft. There are a variety of categories describing the curliness of hair, including straight, wavy, curly, and kinky, among others. The conventional classification of curliness distinguishes three types of hair: African, Caucasian, and Asian. Usually, Asian hair is the thickest, followed by African hair, and then Caucasian hair. An additional feature is the cross-sectional shape of the hair fibers: Caucasian and Asian hairs typically has a similar round shape, with the Asian hair being more cylindrical, while the African hair has a highly elliptical shape.
Today, we can find hair types that would not fit into these three basic categories. Therefore, there are newer classifications developed that categorize hair into more than three groups, regardless of its ethnical origin.
Based on Greasiness
Based on greasiness, two major hair types are usually differentiated- dry and greasy hair.
Dry hair does not contain enough moisture. It is usually a result of damaged cuticle and cortex. Porous cortex cannot retain water; therefore, hair fibers have dull, unhealthy appearance.
Dryness is usually aggravated by excessive shampooing and chemical treatments, such as permanent waving or bleaching. Extremely dry hair needs special care and mild cleansing agents not to worsen the damage.
Greasy hair is usually caused by overactive sebaceous glands, which produce more sebum than normally. Since sebum production is highly influenced by hormones, many consumers experience greasy hair when changes take place in their hormone levels, for example, during puberty. In such cases, the hair may become greasier and need to be washed more often. Greasy hair needs special care because if not cleaned adequately, it can lead to various scalp conditions, such as dandruff.
Hair cleansing
Shampoos are one of the most widely and frequently used personal care products today.
The main benefit of using shampoos is the removal of dirt on the hair. Similarly to dirt on the skin, dirt on the hair consists of sweat, sebum and its breakdown products, dead skin cells, residues of cosmetics and personal care products, dust, and other environmental impurities carried in the air.
Most of these compounds are not soluble in water; therefore, washing the hair with simple water would not be sufficient to remove dirt. Shampoos contain surfactants (similar to skin cleansers), which are able to remove oily particles from the hair.
From the aspect of their chemical nature, shampoos are surfactant-based preparations. Therefore, their cleaning principle is emulsification. Surfactants surround and trap tiny droplets of fat, which in this form can be rinsed off from the hair and scalp. Insoluble particulate soil can be removed by electrostatic repulsion between the soil and the hair fiber assisted by repulsion between the surfactant molecules adsorbed onto the hair fiber and those dissolved in the soil.
Today shampoos are available as liquids, gels, emulsions and powders. Most commonly, shampoos are colloidal dispersions of various surfactants in water. Basic components of a classical shampoo are cleansing agents, thickeners, and water. Usually, various additives are also incorporated in the formulations in order to help the cleansing process, enhance the aesthetic properties, increase foaming, and make the hair shine.
What is the role of surfactants and are they different?
Surfactants aid in cleaning and foaming by reducing the surface tension between two phases. In addition, surfactants can also act as foam boosters and foam stabilizers. Typically, several surfactants are combined to achieve the desired result. For example, shampoos for oily hair contain surfactants with strong sebum removal qualities, unlike those for colored hair that are gentler to the hair. Different surfactants, however, have different characteristics and effects on the hair and scalp. Anionics can make the hair extremely clean, but will leave it with a rough, harsh feeling; while nonionics can increase luster and shine, but they do not foam as well as anionics.
Hair conditioning
Conditioners are applied to the hair after shampooing and are designed to smooth the hair, improve gloss and luster, as well as recondition chemically damaged hair (by permanent waving, hair bleaching, or hot blow-drying), mechanically damaged hair (by excessive brushing), and weathered hair (by sunlight, salty seawater, chlorinated water, or swimming pools).
Conditioners act by reducing static electricity generated after combing dry hair, improving manageability by filling in the gaps around and between the cuticle scales, increasing hair shine by coating hair shafts with a thin layer,decreasing split ends, and improving hair flexibility. Natural sebum is the ideal conditioner. Excessive removal of sebum leads to a harsh and dull appearance of the hair, and it necessitates the use of synthetic sebum-like products.
Conditioners make the hair soft, shiny, and easier to manage. Although the main purpose of using shampoos is to clean the hair, overcleaned hair looks dull and has less shine. Conditioners can be incorporated into shampoos; products containing such ingredients are usually referred to as two-in-one shampoo and conditioner formulations. Conditioners are particularly important in dry hair shampoos and shampoos for colored and bleached hair.
Examples for commonly used ingredients include quats (a type of cationic surfactant); humectants, such as glycerin; proteins; silicones, such as dimethicone)
Fait intéressant
Les cheveux deviennent plus chargés négativement après le brossage. Ces charges négatives se repoussent mutuellement et rendent les cheveux frisés.
Hair is one of the most important features when it comes to first impression and is strongly connected to attractiveness and confidence. Styled, well-kept hair gives the external appearance of being well managed, which in turn can contribute to feeling the same way internally. The key motivator for coloring the hair is graying. Graying can have a significant effect on both men and women, including emotional and psychological stress as well as lowered self-esteem.
Additionally, people are rarely satisfied with their natural hair color. A wide variety of hair coloring products offers an option to everyone to alter their hair color, which can also contribute to self-esteem and confidence.
Nowadays there are different types of hair-coloring products based on the presence or absence of the chemical reaction (known as oxidation) involved in the hair coloring process. Non-oxidative products include temporary dyes and semi-permanent dyes, while demi-permanent dyes, permanent dyes, and hair bleaches fall into the category of oxidative products.
Produits non oxydants
Les produits de cette catégorie ne contiennent pas d'agents oxydants, comme leur nom l'indique. Par conséquent, les colorants non oxydants ne peuvent pas produire des teintes plus claires que la teinte initialement présente et ne peuvent pas assombrir significativement la couleur initialement présente.
Teintures temporaires
Les teintures temporaires ou les rinçages de couleur contiennent généralement des molécules trop grandes pour pénétrer dans le cortex capillaire et ont également une faible affinité pour les cheveux, ce qui signifie que les forces de liaison entre la cuticule des cheveux et les molécules de teinture sont faibles. En conséquence, les teintures temporaires offrent un revêtement faible sur la cuticule des cheveux et se lavent facilement après le premier shampooing. (rinçages de couleur, shampoings rehausseurs de couleur, sprays capillaires, mousses, produits en gel)
Semi-permanent
Les teintures semi-permanentes pour cheveux utilisent généralement des colorants suffisamment petits pour pénétrer dans la cuticule des cheveux dans une certaine mesure, en plus de les teindre de l'extérieur, et, par conséquent, restent sur les cheveux sains pendant 6 à 8 shampooings.
Le pH des teintures semi-permanentes est légèrement alcalin (7.0–9.0), ce qui fait que le cortex gonfle et se soulève. Cela permet un certain degré de pénétration du colorant dans les couches plus profondes de la cuticule. Se laver les cheveux ouvre la cuticule, permettant à la couleur de s'échapper avec le temps en raison de la solubilité des colorants dans l'eau. (lotions, shampooings, gels, crèmes et mousses).
Produits oxydants
Oxidizing hair dyes are two-component systems: one component contains colorless dye and couplers in a highly alkaline formulation. The other component contains hydrogen peroxide (the oxidizing agent, otherwise known as the developer or activator). These products are mixed right before application, which generates a chemical reaction. The alkaline agent swells the hair cuticle and thus helps the penetration of the relatively small dye intermediates into the cortex. In addition, it also destabilizes hydrogen peroxide to liberate oxygen. The oxygen released destroys the hair’s natural melanin (i.e., lightens hair) and also oxidizes the dye intermediates and allows them to react with the couplers within the hair shaft to form a colored molecule. The final color molecule is too large to be removed by shampooing, which makes the color resistant to shampooing. (permanent, demi-permanent dyes, bleachers).
Interesting Fact!
Red shades tend to fade fastest as they have a relatively small molecule size, which can diffuse from the hair and wash away more quickly than other shades.