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.