Hair Growth Phases
Hair growth occurs in three distinct phases. Anagen is the growth phase. Catagen is the regressing phase. Telogen is the resting phase. An additional phase exists, called the Exogen phase. These phases are described below.
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Anagen phaseIn a normal scalp, up to 90% of hair follicles would be in the anagen, or growth, phase. In this phase, the hair follicles are in active growth. The cells inside the roots of the hair are dividing rapidly, and adding to the hair shaft. During this phase, hair typically grows 1 cm every month. The scalp hair remains in this active growth phase for 2-6 years. Genetics determine the amount of time the hair follicle stays in the anagen phase. At the conclusion of the anagen phase, as yet unknown factor causes the follicle to progress into the catagen phase. |
Catagen phase
The catagen phase is a short transition phase that occurs at the end of the anagen phase. This marks the end of active hair growth. This phase lasts for two to three weeks, although can be as quick as one to two weeks.
Telogen phase
This is the resting phase of hair follicles. If your body is subjected to a large amount of stress, up to 70% of hair can enter the telogen phase prematurely. This cases the hair to fall out, and a noticeable amount of hair is shed from the scalp. This condition is called telogen effluvium. the final hair, prior to falling out, is dead and fully keratinized. Normally, 50 to 100 hairs are shed every day from a normal scalp.
Hair growth phase times
In the scalp, the time for each of the above phases varies person to person, and is influenced by a variety of factors, such as different hair color and the shape of the follicle. However, these times are good indicators:
- anagen phase, 4–7 months
- catagen phase, 3–4 weeks
- telogen phase, about 9 months