Many men notice their beard hair has a reddish hue, even when their head hair is a different color like brown, black, or blonde. This common phenomenon is due to the intricate interplay of genetics and pigment production.
The Genetic Blueprint
Hair color is primarily determined by an individual’s genetic makeup. The Melanocortin 1 Receptor (MC1R) gene is central to hair color determination. It provides instructions for creating a protein, the melanocortin 1 receptor, which produces melanin, the pigment that colors skin, hair, and eyes.
Specific variants or mutations in the MC1R gene are largely responsible for red hair. If an individual inherits two mutated versions of the MC1R gene, one from each parent, they typically exhibit red hair across their entire body. This inheritance pattern is described as an autosomal recessive trait. However, carrying just one copy of a mutated MC1R gene can still lead to the appearance of red hair in certain areas, such as facial hair.
The Role of Melanin
The color of human hair is determined by the balance of two primary types of melanin: eumelanin and pheomelanin. Eumelanin is responsible for black and brown pigments. In contrast, pheomelanin imparts red and yellow pigments.
The MC1R gene directly influences the ratio of these two melanin types. When the MC1R receptor functions normally, it activates a pathway that promotes eumelanin production. However, variants in the MC1R gene can reduce or block this activation, causing a shift in pigment production. This leads to a higher concentration of pheomelanin, resulting in the expression of red or reddish tones in the hair. Even those with dark hair possess some pheomelanin, though it is usually concealed by a greater amount of eumelanin.
Why Head Hair Differs from Beard Hair
The color difference between head and beard hair arises because hair follicles in different body areas express genes uniquely. While the MC1R gene variant is present throughout the body, its influence can be more pronounced in facial hair follicles than on the scalp. Even a single mutated copy of the MC1R gene can be sufficient to produce red pigment in facial hair, even when the hair on the head is a different color. This indicates a localized expression of the genetic trait.
Beard hair follicles are also genetically distinct from scalp hair follicles and respond differently to hormonal signals. Beyond MC1R, over 100 other genes are known to influence hair color. The complex interaction of these multiple genes, alongside the MC1R variant, contributes to this localized color variation.