Keratin (/ˈkɛrətɪn/) is one of a family of fibrous structural proteins known as scleroproteins. α-Keratin is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, horns, claws, hooves, calluses, and the outer layer of skin among vertebrates. Keratin also protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, birds, amphibians, and mammals. Excessive keratinization participate in fortification of certain tissues such as in horns of cattle and rhinos, and armadillos' osteoderm. The only other biological matter known to approximate the toughness of keratinized tissue is chitin. Keratin comes in two types, the primitive, softer forms found in all vertebrates and harder, derived forms found only among sauropsids (reptiles and birds). Keratin resists digestion, which is why cats regurgitate hairballs.
Hydrolyzed keratin peptides are derived from natural keratin such as chicken feathers or duck feathers, and are extracted using biological enzyme digestion technology. It has good affinity and moisturizing to the skin. At the same time, it can effectively protect damaged hair, and can effectively repair split hair, reduce and prevent split ends, and at the same time can alleviate the irritation effect of surfactants on skin and hair in cosmetic formulations.
Hair contains a large amount of keratin（about 65% -95%）of the hair. Many natural active proteins have a high affinity for hair, are easily absorbed by the hair, have nutrition and film formation, and are excellent hair conditioning Agents, repair agents and nutrients.