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In the absence of albinism or hyperpigmentation, the human epidermis contains approximately 74% eumelanin and 26% pheomelanin, largely irrespective of skin tone, with eumelanin content ranging between 71.8–78.9%, and pheomelanin varying between 21.1–28.2%. [7]
Eumelanin is found in hair, areola, and skin, and the hair colors gray, black, blond, and brown. In humans, it is more abundant in people with dark skin. Pheomelanin, a pink to red hue is found in particularly large quantities in red hair, [16] the lips, nipples, glans of the penis, and vagina. [17]
Humans with naturally occurring light skin have varied amounts of smaller and sparsely distributed eumelanin and its lighter-coloured relative, pheomelanin. [ 57 ] [ 86 ] The concentration of pheomelanin varies highly within populations from individual to individual, but it is more commonly found among lightly pigmented Europeans, East Asians ...
There are also differences in the quantity and relative amounts of eumelanin and pheomelanin. [13] Pigmentation including tanning is under hormonal control, including the MSH and ACTH peptides that are produced from the precursor proopiomelanocortin. Vitiligo is a skin disease where people lack melanin in certain areas in the skin.
Pheomelanin colors hair orange and red. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color; [4] more black eumelanin leads to blacker hair and more brown eumelanin to browner hair. [6] All human hair has some amount of both pigments. [9] Over 95% of melanin content in black and brown hair is eumelanin ...
A woman with dark skin. Dark skin is a type of human skin color that is rich in melanin pigments. [1] [2] [3] People with dark skin are often referred to as black people, [4] although this usage can be ambiguous in some countries where it is also used to specifically refer to different ethnic groups or populations. [5] [6] [7] [8]
Agouti-signaling protein is a protein that in humans is encoded by the ASIP gene. [5] [6] It is responsible for the distribution of melanin pigment in mammals.[7] [8] Agouti interacts with the melanocortin 1 receptor to determine whether the melanocyte (pigment cell) produces phaeomelanin (a red to yellow pigment), or eumelanin (a brown to black pigment). [9]
Melanin is one of the major absorbers of light in some biological tissue (although its contribution is smaller than other components). There are two types of melanin: eumelanin which is black-brown and pheomelanin which is red-yellow. [8] The molar extinction coefficient spectra corresponding to both types are shown in Figure 3.