Hair turns grey primarily due to a decrease in melanin production within the hair follicles, which is influenced by genetic factors. The process involves pigment cells in the follicles gradually producing less melanin, leading to the loss of color. While grey is the most common color associated with this process, the absence of melanin results in white hair. The discussion suggests that the underlying cause of reduced melanin could be linked to a genetic "clock" that limits production, potentially influenced by environmental factors or chemical agents. Conditions such as AIDS, smoking, or chemotherapy can accelerate greying, indicating that external factors may also play a role in premature greying.
