stem cells

Graying manes: the story of white and gray hair


The process of why hair becomes white still remains a mystery. Much like the skin, hair texture and color can change with time (age). Locks of gray, salt and pepper styles, and stark white manes are inevitable for many. By 50 years of age, 50% of the population has 50% gray hair. The process of “graying” usually starts at the temples in the 3rd decade of life and progress to involve the crown and back of the scalp.

There is an observed relationship of gray occurring in different backgrounds, with Caucasians (redheads) graying earliest, then Asians, then Africa Americans. Stress does not accelerate graying directly; however, chronic wear on the body from stress and nutrition status may affect the production of melanin needed for hair color.

Hair fibers contain melanin, a pigment incorporated into the hair fiber by pigment-producing cells called melanocytes.  The distribution and the type of melanin is what gives the intensity and color to the hair.  Every hair fiber goes through a hair growth cycle. Only hairs in the anagen phase can grow.  This results in the anagen phase being the only time in which melanin can be incorporated into hairs.

In the catagen and telogen phases the hair is resting and shedding, respectively. In these two phases, the hair no longer grows and the melanocytes die or halt their activity.  During the next growth cycle, a message is sent to stimulate the remainder melanocytes or targets a reservoir of stem cells to migrate to the base of the follicle and regenerate melanocytes.

The melanocytes of white hair fibers and follicles have been studied. There are reports indicating that certain check points of melanocyte function are disrupted in white hair fibers. Some melanocytes stopped producing melanin altogether, some were still actively producing melanin but could not transport the melanin to the hair fiber, and some stem cell reservoirs did not migrate to regenerate dying melanocytes, thus creating a white hair.

Hair usually grows with melanin with the exception of certain autoimmune and genetic conditions.  With the reduction of melanin in the hair fiber along with reflective light bouncing off pigmented and non-pigmented white hairs, a gray color can be appreciated. This is the salt and pepper appearance some people have.

Earlier graying can become a genetic component inherited from a parent.  Some individuals never gray which science is still investigating whether there is an environmental component that can delay or prevent the process of graying. Until then, graying is part of the natural process of aging and many choose to embrace this change.




Hair 101: Hair follicles and their life cycle

We are born with roughly 100,000 follicles on our scalp. We cannot regrow or generate new follicles after birth so what we are born with is what we have. Follicles create hair from stem cells that sit near the follicle and produce a new hair bulb (the white part located at the root end of a shed hair and is released with the hair). Over time, we lose follicles through factors such as age, hormone, or genetic follicular miniaturization or scarring disorders that destroy the abovementioned stem cells.

Blondes have roughly 20% more follicles than brunettes and redheads have about 20% fewer follicles. Asians and African Americans have fewer follicles and lower hair density than Caucasians. The follicles on the scalps of Caucasians and Asians are straight. The follicles curl and are on a greater angle on African American scalps. This curled follicle is the reason follicles are more difficult to harvest for hair transplants in African American patients.

Follicles cycle through three natural cycles, a growth phase, a rest phase, and a fall out phase, medically referred to as anagen, catagen, and telogen phases, respectively.  Each follicle individually cycles through these three phases independently of each other. Of those ~100 000 follicles, 85-90% are in anagen, <1% are in catagen, and 10-15% are in the natural fall out phase, telogen.  Follicles stay in the anagen growth phase for 2-6 years, catagen for 2-3 weeks, and telogen for 3 months before the hair is released from the follicle. Applying these numbers, you will shed  on average 100-200 hairs/day.  If these hairs are collected, it can appear as a large amount of hair but be reassured that a fresh new anagen hair helps to push out that old telogen hair and a new follicle cycle begins.

Anagen follicles grow scalp hairs at a rate of 0.35cm/day or roughly 1cm/month. This rate may increase with medications or pregnancy and decrease with age, nutrition, medications, and illnesses. Follicles only create hair in anagen growth phases.  Therefore, hairs only grow in anagen phase, so follicles in the catagen and telogen phase only rest and fall out, respectively.  The maximum length is greatest at the end of anagen phase with the exception of breakage which can shorten hairs. Proper hair care can help maintain length retention. Moisture regimens can be found at

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