Tuesday, November 06, 2007

Hair Growth - How Does Hair Grow?

Hair is formed at the base of a hair follicle. A follicle is a structure resembling a pouch that is located below the skin. What we usually call hair is in reality the hair shaft, which is nothing but the keratinized, hardened tissue that grows from a follicle, which is where hair growth is initiated.

Our head contains thousands of such hair follicles. However, all of them are not active at the same time. It has been observed that not more than 80% of our follicles are producing hair growth at any one time. The remaining 20% of the follicles are asleep or dormant.
When our inactive or dormant hair follicles start working again, they push out an old hair while producing a new one. Our hair grows from the follicle at an average rate of one-half inch every month. The hair growth continues for a period varying between four and seven years, after which there sets in a ‘resting’ phase. After this resting phase, it is time for the hair to fall out. As a hair falls out, a new hair grows in its place after a gap of three weeks to three months. There are chances of us losing 50 to 100 hairs in any day. Some of us lose even more than that, not to get them back again.

Hair grows differently from person to person, depending on age, weight, metabolism, hormones, ethnicity, medications, and some other factors. However, our hair growth effectively covers three distinct phases: anagen, catagen and telogen. The anagen phase is also called the active growth phase. This phase continues for several years. At any given time, the major portion (85%) of our body hair is found to be in this phase.

During this anagen phase, the hair has an abundance of melanin. The catagen or the regressive phase lasts for a period of nearly two weeks, during which the hair stops growing but is not yet shed. It has been observed that about 3 - 4% of our body hair is in this phase at any given time. The telogen phase or the resting phase continues for 5 - 6 weeks, at the end of which the hair falls out and a new hair begins to take shape. Nearly 10-13% of our body hair is in this phase at any given time. There is an extensive loss of hair when more hair enters and stay in this phase. Research works have established that the shock caused to the human system by stress and sickness can result in a larger percentage of hair staying in the resting phase, leading to reduced active hair growth along with an accelerated period of loss of hair.