Understanding the Hair Growth Cycle
Hair grows in a continuous cycle, with each strand at a different stage of development. Understanding this cycle is essential for identifying potential causes for hair loss or thinning, recognizing normal versus abnormal hair shedding, and more.
Anagen: Growth Phase
The anagen phase is the active growth stage, during which hair follicles produce new hair. On average, approximately 85% of a person’s hair is in this phase at any given time. This phase usually lasts anywhere from two to five years (although can be up to seven) , depending on genetics and other factors. Key to understanding hair growth is that the longer the hair remains in the anagen phase, the longer it can grow.
Catagen: Transition Phase
Following the anagen phase, hair enters the catagen stage, a transitional period that lasts about 10 days. During this time, the hair follicle shrinks and detaches from the blood supply, signaling the end of active growth. Less than 5% of hair is typically in this phase at any given time.
Telogen: Resting Phase
Lastly, in the telogen phase, hair remains in place but is no longer actively growing. This stage lasts for approximately two to three months, and about 10-15% of scalp hair is in this phase at any given point in time. Telogen hairs are not actively growing, however they remain in the follicle until they are naturally shed.
Exogen: Shedding Phase
The exogen phase is an extension of the telogen stage, where old hairs are released from the scalp. Shedding 50-100 hairs per day is normal during this phase.
