The Hair Growth Cycle

Understanding hair growth is key to optimising hair growth and minimising hair shedding.

How Does Hair Grow?

To understand how hair grows, we first need to look at its parts. Hair is made up of two parts: the root and the shaft.

The hair shaft is the visible part exposed at the skin’s surface and composed of hard keratin protein. The hair root below is anchored to a pocket of invaginated basal skin (follicle) and contains a ‘bulb’ where the hairs’ cells actively divide. The shaft is dead tissue, while the root is living (which is why it doesn’t hurt when you cut your hair but it hurts when you pull out a hair strand!)

Cycle of Hair growth

Hair growth is cyclical. Each individual hair goes through various phases of this cycle, independent of the surrounding hair. At any given time, each strand is in a different part of the cycle. (It’s a good thing that each of our hair’s cycles are not in sync, otherwise we would shed all of our hair at once!)

Click on each phase to learn more.

The hair growth cycle

Anagen

The active growth phase in which the hair lengthens.

This phase is lasts the longest, but its duration varies with the body site.

Catagen

Brief transitional phase of a few weeks, in which the hair root regresses.

Telogen

Resting phase with no growth.

Usually 10 to 15% of hair is in this phase. During a period of intensive hair loss, up to 30% can be in the telogen phase.

Exogen

Shedding of the existing hair from the follicle with a new hair piercing and emerging from the skin surface.

The hair bulb remains intact all this while, and when the telogen hair sheds a new hair emerges. As new hair is manufactured in the follicle, it pushes out the hair shaft, creating longer hair. Hair grows about 0.3mm to 0.4mm each day, which adds up to around six inches per year.

Common questions

What if most hair are in the shedding phase?

Thankfully, most hair are in the growing (anagen) phase!

The percentage of hair in each phase at any given point in time is proportionate duration of the phase. So since the growth phase (anagen) is the longest, most hair (>85%) are in this phase. While the least (<1%) are in the shortest phase of catagen. And 10 t0 15% are in the resting or telogen phase.

AnagenCatagenTelogen
% of hair>85%1%10 to 15%
duration3 years or more 3 weeks3 months
Why does hair length vary for different people & different body sites for the same person?

People with long hair have a long anagen phase and vice versa.

Eyelashes, eyebrows, and body hair have shorter growth phases than for the hair on your head, which is why they are much shorter than scalp hair.

Moreover, there are many factors that influence the length of the anagen phase, including genetics, nutrition, age and overall health.

Also, there is a general thinning out of hair with age since the length of the anagen decreases.

Is some amount of hair fall normal?

Hair shedding (‘Exogen’) is an natural and normal part of the hair cycle.

It’s completely normal to lose 50 to 100 hairs each day.

Though some amount of hair fall daily is normal, excessive shedding can come in many forms and have many causes. Keep reading to learn more!

Till then, Glow & Grow! 🙂

Published by Dr. Kanya Rani Vashisht

Dermatologist by day. Dreamer by dusk.

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