The Hair Growth Cycle explained
Hair is formed in the hair follicle and grows out of the follicle in a continuous cyclic pattern of growth and rest.
There are three phases in the hair growth cycle:
- Anagen – Growth phase. During this phase, the follicle actively grows hair. It lasts 2 to 8 years.
- Catagen – Degeneration phase. During this phase, the follicle is almost entirely degraded. It lasts 2 to 4 weeks.
- Telogen – Resting phase. During this phase, the follicle rests prior to re-initiation of an anagen phase and the growth of a new hair shaft. It lasts 2 to 4 months.
As the new hair shaft emerges, it pushes out the prior “dead” hair shaft, and the old hair is shed. About 50 to 100 telogen hairs usually are shed every day; these are the hairs we find in our comb, brush and shower drain. About 10 % of scalp hair follicles are normally in the telogen phase at any given time if the scalp is healthy and not affected by any condition that causes hair loss.
Excerpts copied from International Society of Hair Restoration Surgery, www.ISHRS.org, © 2004.