Hair color originates inside the skin on the head, where hairs are attached. Pull on a hair firmly and slowly until it comes out, and you'll notice a small white tube clinging to the end of it. This tube is a clump of cells that fit inside a narrow hole in your scalp, a hair follicle. Hair grows in hair follicles, and the cells that line hair follicles supply the growing hair with color.
A hair grows as cells are added to its bottom. These cells contain a strong protein called keratin, which gives hair its structure. Fingernails are made of keratin too. As more and more cells rich in keratin are added to the bottom of the hair, the older cells are pushed higher in the follicle tube, towards the surface of the scalp. By the time a hair cell has been pushed through the entire follicle tube to the surface of the head, it is dead. Hair is not alive, which is why it does not hurt to cut it! The more cells that are added, the longer the hair grows.
In case you are wondering…Hair grows about 1 cm every month.
Hair does not keep growing and growing forever. Every two to seven years the follicle stops adding keratin cells. The hair stays attached for a few months and then it falls out. Every day,
As people get older, especially when they have lived for fifty years or more, the color cells start to disappear, and there is less melanin to transfer to the growing hairs. We are not sure why these cells disappear. For some people it happens slowly over many years. For other people it happens quickly. Hairs still keep growing, they just don’t have much color in them any more.