Why Does Hair Turn Gray? Is Graying Reversible?

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Why Does Hair Turn Gray
Hair turns gray due to a variety of factors, including age, genetics, environmental factors, stress, diet, and health.

Hair turns gray as a natural part of aging, but there are several other factors that affect when it happens and whether gray hair is reversible.

Why Does Hair Turn Gray?

Natural hair color mainly depends on two types of melanin pigment produced by cells called melanocytes in hair follicles. There is eumelanin, which gives hair black or brown color, and pheomelanin, which causes yellow or red hues. The distribution and ratio of these pigments determine the hair’s exact color, while the absence of melanin results in white or gray hair.

During our hair’s growth cycle, the melanocytes inject pigment into keratinocytes, the cells producing keratin, a protein that forms the hair’s structure. Over time, these melanocytes may become less active or die off, reducing or eliminating the production of melanin, and thereby graying the hair.

Causes of Hair Graying

But, the time for graying isn’t the same for everyone. Many factors affect the process, including genetics, environmental conditions, nutrition, medical conditions and drugs, and stress.

Genetics

Genetics play a significant role in determining when and to what extent your hair will gray. Specific genes influence this process, such as Bcl2 and Bcl-w, which regulate melanocyte survival, and the IRF4 gene, associated with hair color and timing of graying. If your parents or grandparents went gray early, you might expect the same.

Environmental Factors

Environmental stressors, such as pollution, smoking, and ultraviolet light (UV), speed up the hair graying process by producing reactive oxygen species (ROS) that damage melanocytes.

Dietary Factors

Diet is another factor that impacts hair graying. Vitamins B12, D, E, and biotin, as well as minerals like copper and zinc, are essential for hair health and melanin production. A deficiency in these nutrients contributes to premature graying.

Medical Factors

Certain medical conditions also have an association with premature graying. Examples of these conditions include:

  • Vitiligo (which damages melanocytes)
  • Thyroid disorders
  • Pernicious anemia
  • Vitamin B12 deficiency
  • Tuberous sclerosis (an uncommon inherited condition that produces benign tumors)
  • Alopecia areata
  • Neurofibromatosis (Von Recklinghausen’s disease)

Drugs

Medications that affect hormone balance might also influence hair color. Here some examples of medications that potentially alter hair color:

  1. Chemotherapy Drugs: These powerful drugs target rapidly dividing cells, including the cells of hair follicles, which can lead to hair loss (alopecia). The hair that grows back after chemotherapy may have a different color, texture, or thickness.
  2. Tofacitinib: This drug primarily treats rheumatoid arthritis. However, in some cases, it has shown potential in restoring hair color in patients with alopecia areata.
  3. Imatinib (Gleevec): This is a cancer treatment medication that has been reported to cause changes in hair color in some patients, generally darkening the hair.
  4. Antimalarials: Hydroxychloroquine, a common antimalarial medication, can occasionally cause lightening or graying of the hair.
  5. Triiodothyronine (T3) and thyroxine (T4): These thyroid hormones, often used in treating hypothyroidism, have been reported to cause premature graying in some cases.
  6. Phenobarbital, Primidone, and other anti-seizure drugs: These have been reported to cause changes in hair color, usually darkening it.

Some of these drugs darken hair, but when you stop taking them your hair may turn gray or white.

Stress

There is a relationship between stress and gray hair. Stress affects hormones, inflammation, and the behavior of melanocyte stem cells. Chronic stress eventually causes melanocyte stem cell failure, which results in irreversible hair color change. Chronic stress refers to an ongoing situation, such as a long illness, psychological stress, or permanent environmental stressor. Acute stress, such as emotional or physical trauma, may cause gray hair. But, hair sometimes returns to its original color.

Can You Reverse Gray Hair?

Can You Reverse Gray Hair
For the most part, gray hair is not reversible. However, it can revert to its original color in some situations.

Can gray hair revert to its original color? The answer is nuanced.

In some cases, graying is reversible, especially when it’s associated with stress or nutritional deficiencies. For example, re-pigmentation of hair has been observed after the resolution of severe stress or trauma. Similarly, addressing vitamin B12 or other nutritional deficiencies sometimes restores hair color.

The medical field has also seen advancements in treatments that can potentially slow or reverse hair graying. A drug called tofacitinib, primarily used to treat rheumatoid arthritis, has potential in restoring hair color in alopecia patients. However, further research is needed to establish its effectiveness and safety specifically for graying hair.

Usually, gray hair is not reversible after a certain point. Genetics, chronic stress, and environmental factors produce changes that become the new norm.

Why Does Some Hair Turn White Instead of Gray?

Sometimes hair changes from its normal color to white instead of gray. Over time, gray hair tends toward white. What’s going on?

The transition of hair color to gray or white depends on the loss of pigment produced by cells known as melanocytes, which are located in the hair follicles. As we age, the melanocytes gradually become less active and eventually stop producing pigment. When some pigment still remains, the hair appears gray as the dark or light pigments mix with the colorless hair. When there’s a complete loss of pigment, the hair appears white, which is simply hair without any melanin pigment.

The specific shade of gray or white hair a person develops depends on several factors:

  1. Original Hair Color: Darker hair tends to turn gray before becoming white. This is because dark hair has more eumelanin, and it takes longer for the melanocytes to stop producing it completely.
  2. Genetics: The rate at which our hair loses pigment mainly depends on our genes. Some people may go gray or white more quickly or at a younger age based on their genetic makeup.
  3. Environmental Factors: External factors such as stress, smoking, and exposure to certain chemicals accelerate the graying process.

Therefore, the difference between gray and white hair essentially boils down to the degree of pigment loss. Gray hair is in the process of losing its color, while white hair has lost all of its color.

Can Hair Turn Gray (or White) Overnight?

There is a link between stress and hair graying, but the idea that hair can turn gray overnight is more myth than reality. More often, extreme events change hair color over the course of several day to months..

The biological underpinning of this phenomenon was revealed in a study published in 2020. The researchers found that stress activates the sympathetic nervous system (our “fight or flight” response system), which causes permanent damage to the pigment-producing cells in hair follicles.

The reason stress can’t cause your hair to turn gray overnight is due to the way hair grows. Hair color is determined in the follicle before the hair grows out and becomes visible. Once a hair strand has grown out of the scalp, its color cannot be changed. Hence, a sudden or rapid change in hair color is not possible as it would require all the hair to fall out and be replaced with new gray hair, which is an extensive process.

The phenomenon where people perceive a rapid shift to gray hair, often during times of stress, usually relates to a condition called telogen effluvium. This condition causes the darker (older) hairs to fall out preferentially, leaving behind the gray or white hairs and giving the appearance of sudden graying. When the hair that sheds grows back, it may be gray or it may be its original color.

References

  • Nishimura, E. K., Granter, S. R., Fisher, D. E. (2005). “Mechanisms of Hair Graying: Incomplete Melanocyte Stem Cell Maintenance in the Niche.” Science. 307(5710): 720–724. doi:10.1126/science.1099593
  • Panhard, S., Lozano, I., Loussouarn, G. (2012). Greying of the human hair: a worldwide survey, revisiting the ’50’ rule of thumb.” British Journal of Dermatology, 167(4), 865-873. doi:10.1111/j.1365-2133.2012.11095.x
  • Slominski, A., Tobin, D. J., Shibahara, S., Wortsman, J. (2004). “Melanin Pigmentation in Mammalian Skin and Its Hormonal Regulation.” Physiological Reviews. 84(4): 1155–1228. doi:10.1152/physrev.00044.2003
  • Sun, Q., Lee, W., Hu, H. et al. (2023). “Dedifferentiation maintains melanocyte stem cells in a dynamic niche.” Nature. 616: 774–782. doi:10.1038/s41586-023-05960-6
  • Trüeb, R. M. (2015). “The Impact of Oxidative Stress on Hair.” International Journal of Cosmetic Science. 37. Suppl 2: 25-30. doi:10.1111/ics.12286
  • Zhang, B., Ma, S., Rachmin, I. et al. (2020). “Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells.” Nature. 577: 676–681. doi:10.1038/s41586-020-1935-3