Depending on the individual, approximately 5 million hair follicles cover the surface of the body at any given time. Of that total, about 100,000 to 150,000 strands are growing on the head. Surprisingly, blondes usually have more hair on their heads than those with red or darker hair colors. All those millions of hair follicles are developed and in place before a person is born. Biologically, it is impossible to grow more hair after birth—all the hair you are ever going to have is already there when you arrive in this world (Source: “Hair Loss and Hair Restoration,” www. aad. org/public/publications/pamphlets/common_hairloss. html).
Inside the hair follicle, deep below the skin, hair is going through a life cycle all its own. At any given time, each hair on your body is in one of three phases—growing, resting (or dormant), or shedding. The first phase is the anagen (growth) phase. At this point, the hair is very busy developing in the hair follicle, the pocket-like structure that houses the bulbshaped root of the hair. At the very base of this root is an intricate network of capillaries and nerves that feed the developing hair. During the growth stage, each individual hair is formed by rapidly dividing cells that push forward and up through the follicle. As they
multiply and expand, the cells reach the surface, where they die and harden into what we know (and see) as hair. The growth stage can last anywhere from two to six years. During this phase, hair grows an average of about half an inch per month, or six inches per year (but that is only an average and it varies drastically from very active hair growth to very slow growth for different people).
Over the entire growth phase, the hair can reach a length of approximately three feet, about the middle of the back for most women, before it stops growing and proceeds to the catagen (resting) phase. Naturally, there are variations in length potential, and women with tresses six feet long have been reported, but there are also women who can’t grow hair much past their shoulders. The reason for these variations is that the length of hair is genetically predetermined, which explains why some women feel they can never get their hair to grow past a certain point, while other women can’t seem to get to a hairdresser often enough to keep up with the grow-out.
The catagen phase also includes a transition (intermediate) phase. After about three to six years of growth, the hair cells stop reproducing and the growth process is over. For about two to six weeks, the hair just lies around taking it easy while the root slowly moves up to the skin’s surface.
Entering its last phase of life, the hair is ready to literally jump ship and shed. The telo – gen (final) phase is short-lived. At this point the hair root has moved almost to the surface (near the opening of the oil gland), where it is completely separated from the base of the follicle. In a matter of weeks the anagen (growth) stage will begin again at the base of the hair follicle. Hair cells again start dividing and multiplying, generating a new shaft. When the new hair sprouts to the surface, it simply pushes the old hair out of its way. So all that hair collecting on your brush, in the bottom of your drain, or on your clothing—about 25 to 100 hairs a day—is usually hair that has passed from the growth phase through the transition plateau and into the final period of shedding.
At any given time, approximately 88% of scalp hair is in the anagen phase, 1% in the catagen phase, and 11% in the telogen phase. Thankfully, hair is predominantly in the growing phase (at least if male pattern baldness or some other form of hair loss has not started to occur), which explains why we end up having more hair than less, despite the strands we lose daily.
Although everyone’s hair goes through the same life cycle, not all hair is the same; hair has very distinct inherited differences. African hair grows mostly in an alternating curved/ flat sequence that imparts a coiled, corkscrew-like shape to the hair, a form that produces weak spots at every turn. Asian, Native American, and Hispanic hair is straight to slightly wavy, coarse, thick, and almost always black. European and Hindu hair textures vary greatly, from straight to curly, thick to thin, and fine to coarse, and they also have a wide range of colors. Generally, what distinguishes African hair from European or Asian hair is its tight, spiral growth pattern.
(Sources: www. aad. org; Hair Loss: Principles of Diagnosis and Management Alopecia, by Jerry Shapiro, Taylor & Francis Group, December 2001; Disorders of Hair Growth: Diagnosis and Treatment, McGraw-Hill, Inc., 1994; Dermatology Clinics, October 1996, pages 573-583; The Molecular and Structural Biology of Hair, Annals of the New York Academy of Science, 1991.)