The best way to define the catagen phase is by looking at it as a short transition stage. It is the stage where the hair transitions from being a growing, healthy component, into the shedding and replacement phase. The active growth of the hair comes to an end here. While the growth phase may take anywhere between two and eight years, the catagen phase only lasts a few weeks.
What specifically happens?
Even though it is a relatively short period, there are quite a few changes to the hair during the catagen phase. The follicle stops producing hair and the production of pigment stops as well. The hair follicle also begins to shrink, dwindling all the way down to approximately 1/6th of its previous size. The base of the hair follicle begins to move towards the surface of the skin and the dermal papilla breaks away. The hair bulb stays in the skin, and has a new hair form in it.
You may read that the catagen phase is considered ‘complete’ once a club hair is completely formed. When the part of the hair follicle that is breaking off comes into contact with the hair shaft, it is considered the formation of a club hair. Because this cuts off the old hair from the cellular regeneration and blood supply, the hair now transitions into the final phase.
Trademarks of the catagen phase
During this period, the following is true about our hair:
• Our hair disconnects from the blood supply
• The detached follicle will slowly shrink to approximately 15% of its original size
• The production of color pigment by the hair bulbs stops
• When the new hair is formed, the hair bulb is pushed towards the surface
• At any time, you can expect around two to three percent of our hair to be in the catagen phase