Exogenous phase

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.

Features of the exogenous phase:

  • Hair loss : In the exogenous phase, the old hair is completely released from the hair follicle and falls out. This is a natural part of the hair cycle that makes room for new hair growth.
  • Duration : The duration of the exogenous phase can vary, but is relatively short compared to other phases of the hair cycle. On average, a person loses around 50 to 100 hairs per day through this process.
  • Regeneration : Immediately after the old hair falls out, the hair follicle can enter a new anagen phase and begin to form a new hair.

Meaning of the exogenous phase:

  • Hair Renewal : The exogenous phase allows for the continuous renewal of hair by ensuring that old or damaged hair is regularly replaced.
  • Scalp Health : By supporting the natural shedding of old hair, Exogen Phase helps maintain a healthy scalp.
  • Hair Density and Cycle Regulation : The exogenous phase plays a role in regulating hair density and the overall hair cycle by maintaining the balance between hair growth and loss.

Differentiation from pathological hair loss:

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.

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