THE 3 STAGES OF HAIR GROWTH
All hairs, on ALL parts of the body, go through these stages. For some parts of the body, like the head, the phase can last for 6+ years (think Crystal Gayle). For other parts of the body, e.g. the chin, the growth cycle is approximately 1 year. Therefore, if you pluck a hair from your chin, the follicle may not start growing a hair for another 12 months. By that time, the follicular path the hair would normally use to follow the old hair will have closed up creating a "perfect storm" for ingrown hairs. Read below for more than you ever wanted to know about hair growth.
Wikipedia on hair growth:
The three stages of hair growth are the anagen, catagen, and telogen phases. Each strand of hair on the human body is at its own stage of development. Once the cycle is complete, it restarts and a new strand of hair begins to form. The rate or speed of hair growth is about 1.25 centimeters or 0.5 inches per month, or about 15 centimeters or 6 inches per year.
The anagen phase is known as the growth phase. It begins in the papilla and can last up to eight years. The span at which the hair remains in this stage of growth is determined by genetics. The longer the hair stays in the anagen phase, the faster and longer it will grow. During this phase, the cells in the papilla divide to produce new hair fibers, and the follicle buries itself into the dermal layer of the skin to nourish the strand. About 85% of the hairs on one's head are in the anagen phase at any given time.
Signals sent out by the body determine when the anagen phase ends and the catagen phase begins. The catagen phase, also known as the transitional phase, allows the follicle to, in a sense, renew itself. During this time, which lasts about two weeks, the hair follicle shrinks due to disintegration and the papilla detaches and "rests", cutting the hair strand off from its nourishing blood supply. Ultimately, the follicle is 1/6 its original length, causing the hair shaft to be pushed upward. While hair is not growing during this phase, the length of the terminal fibers increase when the follicle pushes them upward.
During the telogen, or resting, phase the hair and follicle remain dormant anywhere from 1–4 months. Ten to fifteen percent of the hairs on one's head are in this phase of growth in any given time. The anagen phase begins again once the telogen phase is complete. The preceding hair strand is pushed up and out by the new, growing strand. The process causes the normal hair loss known as shedding.
The Amazing Human Hair
The Amazing Human Hair