Hair is mostly made of keratin, a kind of structural protein. Aside from hair, the human skin and nails also contain keratin on the external layer. Keratin is fibrous in nature making it an ideal component for the strands or follicles of hair to stay intact. Without keratin, hair can never grow long and strong. In terms of components, keratin is essentially the most important component of hair. Other minor components include water, some lipid substances, and some amounts of melanin pigment. When talking about hair, it is almost entirely made of the protein called keratin.

Keratin, being a protein and fibrous in terms of structure, is needed in every cycle of hair growth. From the initial growth phase up to the phase where hair growth stops, keratin is involved in the process. It is through the keratin component that the follicles will become longer each day. Through its fibrous components, keratin basically builds up each and every strand of hair. From the initial popping out of the hair follicle to its full growth, keratin is essential in giving hair its form and length. Through the keratin component, the other components such as water and lipids are held in place to make each strand strong and healthy.

The keratin component of hair is produced by cells called keratinocytes. These cells are situated in the skin layer called dermal papilla. Under normal conditions, the keratinocytes will produce enough keratin to produce hair strands and allow hair to grow and become healthy and strong. Different people have different hair growth rates depending on the activity of their keratinocytes and their genes. The more active the keratinocytes are, the thicker will hair become. For problems relating to keratin production, hair growth may slow down and existing hair may become unhealthy. With problems like this, some people may seek relief by using hair products that contain keratin to stimulate further hair growth or at restore good hair health.