Even though our hair may not look it when we observe it with the naked eye, it is constantly renewing, regenerating, and being replaced. The hair growth cycle for every hair has a long period of growth and relatively short period of rest. During the rest period of the hair growth cycle, the hairs are still connected to the hair follicle, but have stopped growing completely. After the resting phase is over, a new hair begins to grow as the old hair is shed. Thus, the entire hair growth cycle starts over. We look at the three stages that the growth cycle of a hair consists of.
The growing stage – anagen
This is the actual growing stage of the hair follicle and takes quite a bit longer than most people may assume. The anagen stage will typically last between three to five years.
The intermediate stage – catagen
Hair follicles do not move from the growing stage directly to the resting phase; they go through the intermediate stage known as catagen first. During this phase, the hair follicles are preparing to enter the resting phase. The deeper portions of the hair follicles begin to collapse and the phase only lasts anywhere between one and two weeks.
The resting or shedding phase – telogen
We have come to the end of the line for the hair follicle and arrived at the resting period. This will take anywhere between three and four months and the older hairs begin to fall out, leaving room for newer hairs to grow. The majority of the growth cycle of a hair follicle is taken up by the anagen phase (approximately 90%). At any given time, approximately 10% of the hairs on our head are going through the telogen or catagen phase, which means that they are not actively growing. However, we avoid bald spots during this process because the hair follicles are distributed over the scalp randomly.