Hair growth cycle

Every human being, be it a man or a woman, wants to look good and always seeks approbation. It is obviously for this reason that most of them concentrate on improving their skin texture and complexion, appearance, and body shape. Some people feel that inner beauty is more important; so, they try to enhance that. Actually, every person has a different opinion about “beauty,” as it is rightly said that, “Beauty lies in the eyes of the beholder.” Hair forms an important part of an individual’s physical beauty. Hence, knowing about the physiology of hair is of great value.

It takes about two to six years for every strand of hair to complete its cycle. Our hair is subjected to washing and conditioning or exposed to pollution, various chemicals, and heat very often. These factors damage the hair shaft but they do not affect the follicles. There are three phases in the hair growth cycle. The duration of a particular phase depends on the person’s age, nutrition, hormonal levels, and physiological or pathological factors.

The first phase, or anagen phase, is the growing stage that determines the actual length of the hair. The hair strand grows by about 1 cm in every 28 days. This phase lasts for 2 to 6 years. There is complete regrowth or regeneration of the lower part of the follicle during this phase. New cells push the older ones upward due to constant cell division and multiplication, resulting in hair growth.

The end of the anagen phase is marked by stoppage of hair growth and cellular destruction at the lower end of the follicle. This is the beginning of the second phase, which is also known as the catagen phase. During this phase that lasts for about 2 to 4 weeks, the hair follicle shrinks to one-sixth of its original size due to loss of the extracellular matrix. The melanocytes present in the hair bulb undergo cellular death and hence stop producing melanin, the substance that imparts color to hair.

The telogen phase is a kind of a “pause” in the hair growth cycle and is therefore also known as the resting stage. This phase is known to last for about 3 months before the hair fall off naturally during simple activities like washing and combing. The part of this phase in which the hair is shed is referred to as the exogen phase. In this phase, 50 to 150 strands of hair are lost from the scalp daily. Near about 10 to 15% of the hair are in this phase at a given point of time.