During which phase does the hair growth cycle begin to break down?

The hair growth cycle has three main phases: anagen, catagen, and telogen. The catagen phase is particularly significant because it marks the transitional period where the hair follicle begins to break down. During catagen, the hair stops growing, and the outer root sheath degenerates, leading to the hair being cut off from its blood supply.

In this phase, which lasts for a few weeks, the lower part of the hair follicle is destroyed, and the hair is shed. The breakdown of the hair follicle is a critical part of the cycle, as it prepares the follicle for the next growth phase, the telogen phase, where the hair is at rest.

The anagen phase is the active growth phase of hair, where the follicles are producing new hair. In contrast, the telogen phase is the resting phase and is characterized by the hair being completely removed from the follicle without any breakdown occurring. Edema, which is the swelling caused by fluid accumulation, is not a relevant phase in the hair growth cycle and does not pertain to hair growth or the condition of hair follicles. Therefore, the catagen phase is the correct choice as it represents the point at which the hair growth cycle begins to break down.