The anagen phase is the longest stage of the hair growth cycle. It is the active phase in which your hair follicles rapidly divide to produce new hair strands. This phase can last from four years to four decades, and typically 80% to 90% of your hair is in this stage.
Catagen and Telogen Phases
These stages are transitional phases in the hair growth cycle. During the catagen phase, your hair follicles begin to thin and shorten before entering the resting telogen phase. In the telogen phase, the hair remains attached to the root by a bulb of Keratin, and this phase can last for about two months. These transitions may take several cycles.
The catagen phase follows the anagen phase and marks its conclusion. Hair follicles shrink, enter a quiescent state, experience regression, and lose about one-sixth of their diameter. Eventually, the hair becomes club hairs, which are shed off for new growth.
The telogen phase is the final resting period of the hair follicle. It typically lasts for three months. During this phase, old hairs fall out naturally, and new hairs emerge to replace them. Temporary hair loss may occur due to nutritional depletion, stress, or illness. After the telogen phase, hair will resume growing at its regular rate.
The exogen phase is the release of club fibers from the follicle. It occurs after the telogen phase and lasts for several months. During this phase, the hair follicles shrink, and growth slows down. Around 10% of your hair may be in this stage anytime.