Hair Growth Cycle

Hair growth goes through a cycle with three identified stages – catagen (transitional phase), telogen (resting phase), and anagen (growing phase). Approximately 90% to 95% of hairs are in the anagen phase, and 5% to 10% are in the telogen phase. In the scalp, the anagen growth phase lasts between 2 to 6 years, catagen between 2 to 3 weeks, and telogen between 2 to 3 months.

Anagen Growth Phase

In the anagen phase, hairs grow at a rate of about 1cm per month which slows with age. Length of hair corresponds to the amount of time in the anagen phase. The length of the hair growth cycle is different for different parts of the body. This explains why hair on the head is longer than hair on other parts of the body, such as the eyebrows which only spend 30-45 days in the anagen phase.

Catagen Transition Phase

Catagen is the period of transition between the anagen growth phase and the telogen resting phase. Less than 1% of hairs are in this 2-3 week period at any one time. Changes take place in the structure of the hair follicle and at the end of catagen, telogen phase is entered.

Telogen Resting Phase

Telogen is the resting phase of the hair growth cycle. At the end of the telogen phase, the hair follicles will reenter the anagen growing phase and start growing again. Approximately 5-10% of scalp hair is in the telogen phase at any one time and these follicles are randomly distributed. It is during telogen hairs that hair is normally shed. Approixmately 25-100 hairs are shed each day. Telogen is also the part of the hair cycle which some of the transplanted hairs will enter. Because telogen can last 2-3 months, these hairs will not start regrowing for 2-3 months and therefore it can take 6 months or longer to see the results of hair transplantation.