Exogen, Shedding Phase of the Hair Growth Cycle: Characterization of a Mouse Model

In 2002, researchers characterized the exogen phase of the hair growth cycle, which is the shedding phase, using a mouse model. They developed methods to collect and quantify shed hair, discovering that shedding is most pronounced during the anagen phase and that the shed hair originates from a previous cycle. The study found that the base of shed hair has a unique morphology, suggesting a proteolytic process is involved in shedding. The findings indicate that exogen is a distinct phase, coupled to anagen, and that shedding is not advantageous before new hair has grown. The study did not specify the number of mice used, but it laid the groundwork for future research into the exogen phase.