Which phase of hair growth is referred to as the transitional phase?

The transitional phase of hair growth is known as catagen. During this phase, which typically lasts for a few weeks, hair follicles undergo a short transitional period as they prepare to enter the next stage of the hair growth cycle. In catagen, the hair follicle shrinks and detaches from the dermal papilla, which is crucial for the hair's growth supply. This phase is characterized by a significant reduction in hair follicle activity, and although hair still exists at the surface of the scalp, it is not actively growing.

Understanding the other phases helps to clarify why catagen is identified as the transitional phase. Anagen is the active growth phase where hair cells divide rapidly, leading to hair growth. In contrast, telogen is the resting phase where the hair does not grow but remains attached to the follicle until it eventually sheds. Exogen refers to the phase when the old hair is shed, which can sometimes happen concurrently with the telogen phase. Thus, catagen uniquely represents the transition between anagen and telogen, highlighting its role in the cycle of hair growth.