Final answer:
Hair follicle pigmentation results from two melanin types—eumelanin and pheomelanin. Eumelanin causes darker hair colors, while pheomelanin leads to red hair. These melanins contribute to both hair color and skin protection from UV radiation.
Step-by-step explanation:
The pigmentation of hair follicles is primarily determined by two types of melanin: eumelanin and pheomelanin. Eumelanin is responsible for black and brown colors, while pheomelanin gives hair a red hue. The varying levels of these melanins result not only in different hair colors but also in the capacity to protect the skin from ultraviolet (UV) radiation. Darker hair, indicative of more eumelanin, is often associated with dark-skinned individuals, who tend to produce more melanin overall in response to sun exposure, thereby protecting their skin.
Eumelanin is not solely associated with hair color, as it also plays a critical role in determining skin color. It essentially protects against UV damage by absorbing UV rays, contributing to the darkening of the skin when exposed to sunlight, known as tanning. However, excessive melanin can also affect the body's ability to synthesize vitamin D. Therefore, the production and accumulation of melanin are a balance between protecting the DNA in epidermal cells from UV radiation and ensuring adequate vitamin D production.
The color of one's hair can change over time due to variations in melanin levels, and it's also possible to have multiple hair colors within a single person. Moreover, age-related changes, such as the emergence of gray or white hair, are typically the result of a decrease in melanin production.