Science Behind The Hair Growth And Hair Loss

Hair Growth

Hair is made up of a protein called keratin. This keretin is produced in hair follicles in the outer layer of skin. Hair grows everywhere on the human body except on the palms of our hands, soles of our feet, mucosal surface of genitalia & lips.

According to U.S. center for disese control(CDC), scalp hair grows at the rate of 1.25 cm (half inch) per month. That means normal persons hair grows 6 inches long in an year. Under normal circumstances human hairs are always growing. This growth of the hair takes place in series of phases collectively known as hair cyles.

Hair cycle

Hair on the scalp grows about .3 to .4 mm/day. Unlike other mammals, human hair growth and shedding is random and not seasonal or cyclical. There is three stages of hair growth:-

1. Anagen
2. Catagen
3. Telogen

At any given time, a random number of hairs will be in one of three stages of growth and shedding: anagen, catagen, and telogen.

1. Anagen

In this phase cells in the root of the hair devide rapidly so it is called active phase of the hair cycle. At the time of new hair growth, the previous hair in the same follicle which has stopped growing or no longer in the anagen phase known as club hair, is pushed out by the new growing hair. Eventually this club hair falls off n growth of a new hair sets in.

In this phase the hair grows about 1 cm every 28 days. Scalp hair stays in this active phase of growth means in anagen for around two to six years.

Hairs in few people doesn’t grow beyond a certain lengh that is because of vary short active phase of the growth. While few of them grow very long because they have a long active phase of growth. The short active growth phase of about 30-45 days explains why hairs of arms, legs, eye lashes & eyebrow are not able to beyond a certain length.

2. Catagen

This is a transitional stage in which the hair follicle renew itself and about 3% of hairs are in this phase at any time. This phase lasts for about two to three weeks. In this phase hair looses its blood supply & doesn’t grow further. Growth of the hair stops and the outer root sheath shrinks and attaches to the root of the hair. This leads to formation of what is known as a club hair.

3. Telogen

Telogen is the resting phase for the hair and usually accounts for 6% to 8% of all hairs. This phase lasts for about 100 days for hairs on the scalp and longer for hairs on the eyebrow, eyelash, arm, and leg. In this phase, the hair follicle is completely at rest and the club hair is formed. Pulling out a hair in this phase will reveal a solid, hard, dry, white material at the root. About 25 to 100 telogen hairs are shed normally each day. In the end of telogen phase the new growing hair pushes out the telogen hair & the anagen phase starts for that follicle.

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Disclaimer:The content published on this website(hairtransplantdelhi.org) is meant to spread awareness and educate the concerned patients regarding baldness and hair transplants as well as the treatment options available for baldness and hair transplant treatment in Delhi India. Any information on the website shall not be regarded as a prescription from a professional dermatologist. We recommend visiting a dermatologist in person for the right diagnosis and the treatment for any hair issues. We do not guarantee specific results as the treatments and the results vary from person to person.

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Hair Growth

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