The Life Cycle Of Human Hair

. 3 min read

During the natural course of evolution in life, your body goes through multiple changes as you grow older. Growing and falling of hair is one of the most common experiences - there is nothing you can do to stop this natural process. However, in today’s life with extremely high stress-levels and increasing pollution, hair loss is a common issue that can affect any of our lives. Before going into the details of different types of hair fall conditions, let us take a deeper dive into the life cycle of human hair.

Life Cycle of Human Hair:

Each strand of hair, although surrounded by thousands of other similar strands, lives a unique life of its own. Interestingly, all strands go through the same phases of growth and eventually die but not at the same time. In other words, when you see few strands falling off your head, other strands of hair are actually at different stages of their lives. As a result, you do not see much of a difference in your locks of hair, even though you lose almost 50-100 strands everyday due to the natural process of hair fall.

In theory, had all your hair been through the same stages of life simultaneously, you would go bald systematically at a certain point of time and have full set of hair at an other point of time. Evidently, that is not what happens to any of us in real life.

The life span of a hair is divided into 3 phases – Anagen, Catagen and Telogen. Each strand goes through these phases and repeats the cycle approximately 20-30 times during a lifetime.

Phase 1 – Anagen:
Duration: 2-4 years
Details: This is the first phase in a hair’s life. The anagen phase is actually the active growth phase of your hair. During this phase, cells beneath the hair follicles get multiplied rapidly, thereby, generating hair bulbs. At this point, the bulb produces new hair fibre which pushes the follicle up and eventually emerges out of your scalp.

During the anagen phase, your hair grows approximately 1 cm per month. The active growth phase of hair is different for different types of hair in your body. Generally, the hair on your arms, legs, eyelashes have significantly shorter growth phase (approx. 30 – 40 days) compared to that on your scalp. This explains the shorter length of hair on these areas.

At any given point of time, a normal scalp contains around 90% of hair in growth phase.

Phase 2 – Catagen:
Duration: 3-4 weeks
Details: This next phase is called catagen or resting phase. During this phase your hair ceases to grow but stays attached to the follicle. The cell division activity in the hair bulb stops leading to degeneration of keratinocyte in the bulbs. The volume of the bulb decreases and it starts to go up towards the epidermis which is the outermost layer of your skin.

During this transitional phase, your hair does not get nutrition from its root and eventually dies.

About 3-4% of your entire scalp hair is in catagen phase at any time.

Phase 3 – Telogen:
Duration: 3-4 months
Details: The last and final phase is called telogen which signifies the detachment of dead hair from the follicle. After catagen phase, when the bulb reaches almost the end of epidermis, your hair strand is loosely bound to its follicle. Any gentle brushing or washing may cause the dead hair to fall out of the scalp. This is a perfectly normal and inevitable phenomenon for each hair at the end of its life.

Once the hair falls out, the bulb slowly retracts from the scalp and establishes back its connection with the dermal papilla which is the inner layer of the skin. At this point, the hair bulbs become ready to start its anagen phase.

This entire life-cycle of a hair continues repeatedly for approximately 20 to 30 times with the duration of each cycle being around 3-5 years.

At any time, 6-7% of your hair are going through telogen phase resulting in 100-150 hair strands to fall out on a daily basis.

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