The Hair Cell Cycle

The hair cell cycle is a continuous process of growth, rest, and renewal that occurs in hair follicles. This cycle is divided into three main phases: anagen, catagen, and telogen. Each phase plays a distinct role in the development and shedding of hair. Understanding the hair cell cycle is crucial for those interested in hair health, growth, and treatment.


Key Phases of the Hair Cell Cycle:

1. Anagen Phase (Growth Phase):

Description: This is the active growth phase where hair follicles are rapidly producing new cells. The hair shaft is continuously formed and pushed upward.

Duration: Typically lasts between two to six years for scalp hair, which determines the maximum length of hair.

Percentage of Follicles: About 85-90% of hair follicles on the scalp are in the anagen phase at any given time.

2. Catagen Phase (Transitional Phase):

Description: This is a short transitional phase marking the end of active hair growth. The hair follicle shrinks and detaches from the blood supply.

Duration: Lasts about two to three weeks.

Percentage of Follicles: Around 1-2% of hair follicles are in the catagen phase at any given time.

3. Telogen Phase (Resting Phase):

Description: During this phase, hair growth stops, and the hair follicle rests. The old hair is gradually pushed out by new hair growing in the anagen phase.

Duration: Lasts about three to four months.

Percentage of Follicles: Approximately 10-15% of hair follicles are in the telogen phase at any given time.


Additional Phase: Exogen

Exogen Phase (Shedding Phase):

Description: Some experts consider exogen a separate phase. It involves the shedding of the old hair that was in the telogen phase. This shedding is a normal part of the cycle and makes room for new hair to emerge from the follicle.

Duration: Overlaps with the late telogen and early anagen phases.


Factors Influencing the Hair Cell Cycle:

1. Genetics: Determines the duration of each phase and the overall hair growth pattern.

2. Hormonal Changes: Hormonal imbalances, such as those experienced during pregnancy or menopause, can affect the hair cycle.

3. Health and Nutrition: Adequate intake of vitamins and minerals supports a healthy hair cycle. Deficiencies can disrupt the cycle and lead to hair loss.

4. Stress and Medical Conditions: Chronic stress, illnesses, and certain medications can interfere with the normal hair cycle, potentially causing hair thinning or loss.



Understanding the hair cell cycle is essential for anyone looking to improve their hair health and growth. By recognizing the different phases and the factors that influence them, you can take steps to maintain a healthy cycle and promote optimal hair growth. Whether you’re dealing with hair loss or simply aiming for healthier hair, this knowledge is the foundation for effective hair care and treatment strategies.

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