Knowing your hair's cycle may help to understand issues you are having with your own hair. Between starting to grow and falling out years later, each hair passes through three distinct phases: The anagen phase (the growing phase), the catagen phase (the intermediate phase), and the telogen phase (the shedding phase).
Hair growth cycle
Anagen
The anagen phase or "the growing phase" is when all new hair growth occurs. During this phase, 90% of the hairs on your head will be growing at their normal rate. This rate on average, is one-half inch per month for most people. Each specific strand of hair can be in the anagen phase for an average of three to five years, but in some cases, up to ten. Throughout this phase, pigment (melanin) is made in the hair follicle. In older people less pigment is created during this stage, hinting to why, white hair starts to appear even if the hair is still growing healthy and strong.
Catagen
The catagen phase or "the transitional phase", signals the end of the growth phase for your hair. During this phase, the hair follicle contracts and detaches from its nutritional supply, the dermal papilla, forming into a rounded club. No pigment is made during this phase and the follicle stops producing hair. The follicle then moves upward toward the surface of the skin. Less than 1% of your hair will be in the catagen phase at any given time. This phase usually only lasts one or two weeks.
Telogen
The telogen phase or "the shedding phase" is the final phase in your hair growth cycle, lasting until the fully-grown hair is shed. It usually lasts for three or four months. During this time, new hair will begin to grow from the hair follicles and old hair will shed naturally or may be pulled out, painlessly and easily, while shampooing or brushing. At any given time, around one in ten of the follicles on your head are in the shedding phase. In other words, 10% of your hair remains in the telogen phase. Your new hair will emerge from the same opening as the old one, at the surface of the skin, to begin its three-step cycle again!
All three stages of this
hair growth cycle repeat on an average of every four to five years. This means that if your hair averages a four year anagen phase, and you trim it one half inch every three months, you can expect your hair to grow four inches each year, or a total of sixteen inches before it reaches the catagen phase.
