Hair turns gray when pigment cells in the hair follicles produce less melanin, which is mostly genetic and increases with age.
Why
Hair follicles contain melanocytes, which make melanin. With age, they make less melanin and hair turns gray, then white.
When
Many people see grays in their mid 30s. Genetics decide when.
Other causes
- Stress (can speed it, per a 2020 Harvard study).
- Smoking.
- Vitamin B12 deficiency.
- Thyroid conditions and vitiligo.
Can it be reversed
Usually no, unless due to a deficiency.
Hair pigment
Hair color comes from melanin made by melanocytes in the hair follicles. With age, melanocyte stem cells decline, and the follicles produce less melanin. Hair then looks gray or white because it lacks pigment. A 2020 study in Nature reported that stress can deplete these stem cells in mice.
Typical timing
Genetics largely determine when it starts. On average, people begin to see gray hairs in their mid 30s for Caucasians, late 30s for Asians and mid 40s for Africans, according to a rule of thumb. The “rule of 50” says that about 50% of people have 50% gray hair by age 50. Gray hair before age 20 in people of European descent, or before 30 in people of African descent, is considered premature.
Other causes
- Smoking, which is linked to premature graying in studies.
- Stress (supported by animal studies and some human reports).
- Vitamin B12, vitamin D, copper and iron deficiencies.
- Thyroid disease.
- Autoimmune conditions: vitiligo and alopecia areata (which can leave gray or white hair).
- Genetic syndromes.
- Chemotherapy.
Can it be reversed
Genetically determined graying cannot be reversed. If due to a nutritional deficiency or thyroid problem, correcting it may restore some color. A 2020 study from Columbia University published in eLife found that individual hairs can regain color when stress is reduced, but this was small scale research.
Care
Gray hair is coarser and drier. Use moisturizing products and protect from sun.
Options
Dyes, semi permanent color, highlights or embracing silver.
When to see a doctor
If gray hair appears suddenly or at a very young age, or with fatigue, weakness or skin changes.
Why hair loses color
Hair color comes from melanin made by melanocytes in hair follicles. With age, melanocyte stem cells decline, so new hair grows without pigment. The timing is largely genetic: many people see first grays in their mid 30s for Caucasians, late 30s for Asians and mid 40s for people of African descent, on average. Stress, smoking and some nutrient deficiencies such as vitamin B12 are associated with earlier graying.
Management
A 2020 study in eLife by researchers at the Columbia University found that stress related graying can be partly reversible when stress is removed. Most gray hair cannot be reversed with supplements. Dyes, semi permanent colors and gray blending are common options. Premature graying before 20 in Caucasians can sometimes relate to thyroid, vitiligo or autoimmune conditions and is worth discussing with a doctor.
Based on data from the National Institutes of Health and eLife
