What causes human hair to turn grey?

Human hair turns grey due to a decrease in the production of melanin, the pigment that gives hair its colour. Melanocytes, the cells that produce melanin, gradually decline in number and activity as we age. Several factors contribute to this process, including:

1. Genetics: Grey hair is often influenced by genetics. People with a family history of premature greying are more likely to experience it themselves.

2. Age: Age is the most significant factor in greying hair. As we age, the production of melanin slows down, resulting in a gradual reduction of hair colour.

3. Stress: Chronic stress has been linked to premature greying. Mental and physical stress can cause changes in the hair growth cycle and affect melanin production.

4. Medical Conditions: Certain medical conditions, such as thyroid disorders, anaemia, and vitiligo, can disrupt melanin production and cause premature greying.

5. Autoimmune Disorders: Autoimmune conditions like alopecia areata and autoimmune thyroiditis can target the hair follicles and melanocytes, leading to loss of hair colour.

6. Smoking: Smoking has been associated with premature greying due to the oxidative stress and damage it causes to cells, including those responsible for melanin production.

7. Nutritional Deficiencies: Lack of certain nutrients, such as vitamin B12, vitamin D, copper, and iron, can impair melanin production and contribute to greying hair.

While the underlying mechanisms of greying hair are still being studied, these are some of the primary factors that influence this natural process.