What is the Hair Growth Cycle?

Our hair follicles undergo a life-long cyclical transformation that allows hair strands to grow and shed. The cycle includes four distinct phases: anagen, catagen, telogen, and exogen.

Anagen Phase

Known as the “growth phase,” the anagen phase can last 2-7 years and determines the hair’s length before it falls out. In this phase, cells in the hair follicle divide rapidly, producing a protein called keratin, and move upward to form the hair strand. Typically, 85-90% of hair follicles are in this growth phase at any given time. 

Catagen Phase

Known as the “transition phase,” the catagen phase can last around 2-3 weeks. Hair stops growing and becomes detached from the base of the follicle. This phase is a brief transition period where the hair strand stops growing, and the follicle undergoes changes to prepare for the resting phase. Usually, only 1-2% of hair follicles are in this phase simultaneously. 

Telogen Phase

Known as the “resting phase,” the telogen phase can last for 3-4 months. During this phase, the transformed hair follicle no longer receives the nutrients it needs to grow hair. The hair strand remains in the follicle but becomes detached from the skin. Typically, 10-15% of hair follicles are in this resting phase at any given time. Stress can cause the hair follicles to prematurely enter this phase, leading to shedding.

Exogen Phase

Known as the “shedding phase,” the exogen phase can last 2-4 months. This phase is when the hair strand finally sheds, marking the end of the hair growth cycle. After shedding, the hair follicle re-enters the growth phase (anagen) and begins a new cycle.

Hair follicles are micro-organs, and much like any other organ, they are directly and indirectly impacted by the interconnected systems in the body. Changes in any of these systems—whether triggered by stress, hormones, aging, lifestyle, nutrition, or metabolism—can affect the hair growth cycle. Imbalances in the body can signal the hair follicle to prematurely stop growing, resulting in shedding, as well as shorten the growth phase, delay new growth, and cause hairs to prematurely enter the telogen (resting) phase, where hair sheds more easily.