What phase is the active growth stage of hair called?

The active growth stage of hair is known as the anagen phase. During this phase, the hair follicles are engaged in robust cell division, which leads to hair strands growing longer and thicker. This period can vary in duration depending on factors such as an individual's genetics and the location of the hair on the body; for example, scalp hair remains in this phase for several years, leading to longer hair growth.

In contrast, the telogen phase is a resting phase where the hair is not actively growing, and the hair follicles prepare to shed the hair strand. The catagen phase represents a transitional phase where hair growth slows down, and the follicle prepares to enter the resting phase. The resting phase is another term for the telogen phase, during which hair remains in the follicle without growth until it is eventually shed and replaced by new hair from the anagen phase again.

Understanding the anagen phase is crucial for those involved in hair treatments and laser practices, as it determines when a hair is most susceptible to treatments aimed at permanent reduction or removal.