It’s essential to understand the hair growth cycle in order to recognize and understand many of the problems you can encounter with your hair. The hair growth cycle consists of three distinct stages – anagen, catagen and telogen.
Each hair has its own life cycle. The first phase of the Hair Cycle is the ‘Anagen’ phase, precisely, the growing phase. Hair grows at about 1.25 cm each month and last between 2 to 6 years.
This is followed by a transitional stage. It signals the end of the active growth of a hair, and is formally called Catagen phase. During this time, which lasts about two weeks, the hair follicle shrinks due to disintegration, detaches from the hair shaft and “rests,” cutting the hair strand off from its nourishing blood supply. This phase normally lasts 2 to 3 weeks.
At the end of the transitional phase, the hair is shed and the follicle starts to grow a new one. At any moment, about 85-90% of the hair follicles of the scalp are in growing hair in the first phase; only about 10-15% are in the resting phase; and this resting phase is called the Telogen phase during which the follicle remains dormant anywhere from 1–4 months. The anagen phase begins again once the telogen phase is complete. The process results in normal hair loss known as shedding.
All three phases occur simultaneously; one strand of hair may be in the anagen phase, while another is in the telogen phase. If a follicle is destroyed for any reason, no new hair will grow from it.
Hair loss, hair thinning and problems with hair growth occur when your growth cycle is disrupted. This can be triggered by conditions such as metabolic imbalances, illness or improper nutrition.
For instance, 6 weeks after restrictive dieting or a high fever you can experience telogen effluvium (diffuse hair fall). This occurs when your anagen phase is cut short and many hairs enter the telogen phase all at the same time. If your hair growth cycle is constantly challenged, or not supported, you may find that your hair won’t grow as long as it used to. This is because your hair is never allowed to stay in the anagen (growing) phase long enough for your hairs to reach the desired length.