The exogenous phase is the final part of the hair cycle, a phase in which the hair is expelled from the follicle. The human hair cycle consists of three main phases: anagen (growth phase), catagen (transitional phase) and telogen (resting phase), followed by the exogenous phase. While the first three phases are well documented and understood, the exogenous phase as a distinct phase has only been studied and recognized in more detail in recent decades.
Although exogenous phase hair loss is a natural process, a significant increase in hair loss can indicate problems. Conditions like telogens Effluvium, in which a larger number of hairs prematurely fall into the Telogen phase occurs and consequently falls out, can lead to visible hair loss. Differences in the density, speed and pattern of hair loss are key indicators that help distinguish normal cyclic processes from pathological hair loss.
In dermatology and Trichology Understanding the entire hair cycle, including the exogenous phase, is crucial for the diagnosis and treatment of hair and scalp diseases. Treatment approaches may aim to support the normal hair cycle or correct disorders that cause unusual hair loss.
