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 …
