Most of the hair on our scalp is in a growing phase that lasts from two to six years. A transitional phase lasts three weeks followed by a resting phase. The resting phase ends after two to four months when the old hair is pushed out by a new hair growing from the same bulb. The hair on our eyelashes, trunk, arms and legs only grows from one to six months before the resting stage begins. Collectively you produce 1.2 inches per minute or 37 miles worth per year.
Hair loss is normal.
We lose 50 to 100 hairs a day. Disease is one of the things that can interrupt the normal pattern. Usually the hair is replaced by new growth and the normal replacement cycle is reestablished. During pregnancy, hair loss is slowed. Childbirth triggers many hairs of the mother to enter the resting phase of the hair cycle.