The telogen phase is the third phase of the hair’s cycle, occurring after both the anagen phase and catagen phase. It typically lasts between three to five months. During this final stage of a hair’s lifecycle, the hair ceases to grow any further and it becomes fully keratinized. The dermal papilla enters a resting state and does not supply any nutrition to the hair, which is fully grown and no longer needs sustenance.
A club hair is a hair that has matured and no longer has access to the blood supply because there is no longer a need to grow. Instead, the hair bulb is now made of keratin, and is ready to make an exit off of the scalp so that the anagen phase can start anew. As such, it is not uncommon to lose around a hundred of these special types of hair every day.
In the previous stage, known as the catagen phase, the follicle shrinks rapidly to cut off the hair shaft from the blood supply. During this next phase, the hair follicle relocates and restructures its cells towards the bottom of the hair fiber itself, effectively anchoring the hair at the base. Although the hair has long stopped growing and is now dead, it is still being held into place by this clump of discarded cells. Towards the end of this phase, a new hair follicle begins to form overtop of the old, shrunken one. This new hair follicle grows downward and expands. In doing so, the anchoring point at the base of the hair weakens, and the hair can quite easily break away to leave the scalp. An enlarged follicle also allows the hair to pass more easily. This process of losing club hairs is known as shedding.
In addition to having a shorter anagen (growth) phase, body hair typically stays in the telogen phase for much longer than hair on the scalp. This means that body hair is not permitted to grow for very long when compared to scalp hair, and also spends more time cut away from the blood supply, too. These are the two primary reasons why humans are not covered in more body hair. In fact, unlike most animals, all hair on the human body and scalp is constantly going through one of the various life cycles outlined here on an individual and completely separate basis.
It is completely normal for a small portion of hair to be going through the telogen phase at any given time, with some estimates placing it up to nearly 20% of all hair on top of the head. However, when an overwhelming number of hairs go into this phase at the same time, it can create a disorder. These disorders can be caused by external factors, such as stress or the environment, or they can be genetically inherited.
The naturally occurring steroid known as DHT is thought to prolong the telogen phase over time, lessening the hair’s ability to remain in the anagen phase and grow.