The catagen phase, also known as the transition phase, is the second part of the hair growth cycle and immediately follows the Anagen phase. During this phase, the hair stops growing and prepares for the next cycle. The duration of the catagen phase is usually only two to three weeks.
During the catagen phase, the hair root together and is cut off from the blood supply. This causes the hair follicle cells to become inactive and stop producing new hair. At the same time, at the transition area between the hair root and the hair shaft structural changes that weaken the hair.
About 3% of all hair is in the catagen phase at any given time. This means that a small portion of the hair is in a state of transition while the rest is in anagen or Telogen phase is.
Although hair does not actively grow during the catagen phase, it still remains anchored to the scalp. During this time, hair is particularly vulnerable to hair loss as it is no longer supplied with nutrients and is weakened.
After the catagen phase, the hair enters the telogen phase, the resting phase of the hair cycle. At this stage the hair is released and eventually falls out to make room for a new hair.
In summary, the catagen phase is the transition phase of the hair growth cycle in which the hair stops growing and prepares for the next cycle. This phase usually only lasts a few weeks and is characterized by inactivity of the hair follicle cells. During this time, the hair is weakened and prone to hair loss.
