It is now an ingredient that can no longer be ignored in hair care: shampoos, conditioners, masks or serums "enriched with keratin". It is the basis of the Brazilian straightening; it is present in some skin cares, and, more frequently, in nail cares … By the way, what is exactly keratin? Where does it come from, what does it do? A trip in the fibrous core of a trendy active ingredient.
Keratin is a protein, helical and fiber-like, made of long chains of sulfurised amino-acids (mainly, cysteine and methionine).
Keratin at every extremity
Keratin is natural, synthesized by many living bodies, especially mammals, humans and animals. It is an element common to all the skin appendages, i.e. the production of skin cells: thus, it is an element of claws, horns, beaks or hooves of animals, as well as human skin, nails, hair. Indeed, hair is 95% made of keratin.
There are two kinds of keratin, based on their structures:
• with a coherent structure, the "hard" keratin, high in sulfur, makes nails and hair,
• with a more supple structure and lower in sulfur, the "soft" keratin is found mainly on the epidermis.
Further, its fibers are ranged after different directions, depending on the structure that retains them:
• in hair, they are aligned along a vertical axis, and are linked to each other by sulfur molecules at 90° of the main direction. They are called "disulfide bonds". This structure gives the material its coherence and its resilience,
• in nails, the fibers are along a transverse direction,
• in the stratum corneum, they come in all the directions.
Keratin: the life of a dead substance
In humans, keratin is produced by keratinocytes, cells deep-rooted in the epidermis.
On the skin level, following a constant process, cells of the epidermis go up to the surface as they are replaced by new cells. There, they dry, harden and thicken, then die, giving rise to the stratum corneum, which flakes and is wiped off naturally. This hardening comes with the keratin production.
The hair bulb, made of similar cells, ages along the same process. The "old" cells, going to the surface to let some space to the new ones, are "pushed" to the outside and make a hair. A hair is, therefore, is a mass of "keratinized" cells, in other words … a mass of dead cells.
Dead, yes, but which make a supple material, which seems to be living, and not that unalterable …
Further, keep in mind that we are not all the same regarding the production of keratin. Depending on genetic and ethnic peculiarities, its fibers may be more or less thick, more or less supple … which is why Asian peoples’ hair are generally thicker and straighter than hair of Western peoples!
Keratin and its gifted fiber
It seems so simple, a fibrous protein, high in amino-acids … nevertheless, keratin has many different properties, some of them very useful for us, including for our beauty.
It likes water. It draws it and soaks it as a sponge when possible. It can absorb water up to its 40% by weight.
Whereas our skin could be happy with that and be more moisturized, some hair does not like the change of hair-dressing due to a humid atmosphere … especially when prone to frizz. However, some may get a very nice volume …
Helical, keratin fibers wind up together, as a kind of spring. With the same effect: one may pull (reasonably!) hair without breaking it. They stretch a bit … and come back to their original length as soon as the pulling is ended.
Resilient, but malleable
Thanks to its strong structure (though elastic at the same time), keratin does not break easily. Nevertheless, it can easily take another shape, at least temporarily, for instance, when heated: indeed, this is the core principle of the brushing to shape a frizz or to straighten with a brush and to stabilize them with the heat from the hair-dryer.
A radiance factor
A problem-free and well-balanced keratin allows for the organizing of the hair flakes to give a perfectly even and smooth surface … able to reflect light efficiently and to give hair a radiant aspect. On the contrary, when flakes are less well connected, hair will be dull and tired.
Keratin as a support to cosmetics
The cosmetic industry knows how to be opportunist, and to use the keratin properties to its own benefit.
The natural colour of keratin (your hair colour) may be modified, thanks to its hydrophilic properties. The process is "simple": open the flakes with an alkaline product to give access to the keratin, soak it with a liquid colourant with the wanted colour. Then, "reconnect" the flakes so that the colourant is entrapped in fibers. The result is guaranteed … until new keratinized cells arrive, needing a new treatment to "mask the roots".
It is also possible to use the keratin malleability to modify the shape of hair for longer than a mere brushing is able to do. Uncurling, perms and straightening are the best examples.
The disulfide bonds, which "glue" the keratin fibers have to be broken. Thus, hair has no shape of its own. One has "only" to set the required shape, then to join back the disulfide bonds. This is a lot of aggressive chemistry, which, if regularly applied, may make keratin fragile, hence dull and brittle hair.
Keratin, active ingredient for cosmetics
It is quite easy to modify the properties of the endogenous keratin (the keratin of our own body). However, the cosmetic industry does not stop there. More and more often, it designs products, especially for nail care and hair care, which bring keratin from the outside. Nevertheless, does the exogenous keratin (that coming from external sources) bring the same benefits as those given by our own keratin?
The marketing keratin
The sales points on the labels describe the marvelous world brought by keratin (raw, or more often hydrolyzed) in cosmetic products: nourishing, restructuring, repairing, moisturizing, smoothening, tonifying hair fibers … Shall we trust them?
Based on the pieces of information we have collected … not that much.
Indeed, this large molecule can, in no way, go through the epidermis barrier nor enter a hair whose flakes are well bound … Its effect, only on the surface, is to give the hair fiber a sheath, to let a thin film on a nail or on the skin. Far from the promised effects, even if a purely cosmetic effect is seeable …
On the other hand, what keratin can do, only in some circumstances, is the release of its amino-acids, which will then be interesting to nurture the cutaneous tissue and help repairing it.
Where does this active ingredient come from, when used in our cosmetics?
Sometimes, labels state that it is natural. This must be understood as: usually extracted from the horns and hooves of animals killed in slaughter-houses, more often now, from the feathers of poultry …
This kind of keratin, obviously, is not found in organic-labelled cosmetics, as animal extracts are banned in such products.
Sheep wool is sometimes used as “"rganic-compatible" (it is available without killing the animal that produces it, or without any animal- suffering), though it is not yet widely used).
As this active ingredient is trendy, alternatives to animal keratin have been looked for. It could be available from vegetable sources. In fact, this phytokeratin is a complex blend of wheat proteins (gluten), soybean and corn proteins.
Not that bad, as its content in amino-acids and their respective quantities are quite close to the one found in our nails and hair. Knowing that, this exogenous origin may be as good as the animal origin.
Except for a difference: phytokeratin is structurally different from the "true" keratin, and it does not allow for the same strengthening-sheathing effect. Nevertheless, we are sure that the "keratin-like" trend, so efficiently used by the marketing departments, is here to stay for the foreseeable future.