Hair Growth Cycle
Ever feel like you are suddenly losing your hair or that sometimes you seem to have more hair than ever? It's true, actually. Depending on the time of year and phase of hair growth, you do have more or less hair than before. These cycles determine how much hair you have and how much you are losing at any given time. Each hair follicle comes from a nurturing bulb under the skin. Along with the bulb are sebaceous and sweat glands and a blood supply.
Your hair grows in a three-part cycle composed of the anagen, catagen and telogen phases.
During the anagen phase, your hair is in a growth period that lasts for three to seven years, depending on what kind of hair it is. Our eyebrows and eyelashes have a shorter growth cycle, consisting of only months, and therefore they have a shorter overall length. Scalp hair has a long growth cycle and can give the impression of endless possible length. About eighty-five percent of the hair follicles on your scalp are in the anagen phase, growing at about half an inch a month. During this time, the hair bulb produces your hair pigment, the blood supply provides nutrients and minerals to your hair and your hair looks thick and nourished.
After the anagen phase comes the much shorter catagen phase, lasting between two and four weeks. This is the recession phase, when your hair detaches from the blood supply and shrinks to about one-sixth its anagen size. At this point, the bulb stops producing the color pigment and rises toward the surface of the skin, allowing the hair to fall out during the telogen phase. Only about two or three percent of your hair is in the catagen phase at any given time.
The final phase of your hair's growth is the telogen phase. This is the resting phase, when your hair follicle, the part of the hair shaft that is under the skin, falls out at a rate of fifty to one hundred hairs per day. Ten to fifteen percent of your scalp hair is in the telogen phase, which lasts for about three months. The hair in this cycle is weak, thin and easily removed through brushing or pulling through a ponytail or even running your fingers through your hair. This phase is followed by the anagen, growth stage, and the empty and resting bulbs grow a new follicle of hair.