How Long Does a Hair Live?
Hairs do not live forever. In fact, they hardly live at all. The base of a hair is called the root, and nestles inside a tiny pit in the skin called a hair follicle. Cells in the follicle multiply and add to the root. They fill with hard keratin, glue themselves together into a rod shape, and rapidly die. The rest of the hair, called the shaft, is gradually pushed upwards in the process. A single scalp hair grows like this for about three years. Then it falls out and the follicle rests for up to six months, before sprouting a new hair. Luckily, this natural replacement happens at different times all over the scalp, rather than all at once. About 100 old hairs are lost daily and 100 new ones appear.