Permanently white hair starting in childhood can be genetically inherited, but unlike albinism, there are no negative medical implications. : 867Įuropeans often begin to grow gray hairs in their mid-30s while Asians begin graying in their late 30s, but most Africans retain their original hair color until their mid-40s.
Piebaldism is a rare autosomal dominant disorder of melanocyte development, which may cause a congenital white forelock. At some point in the human life cycle, cells that are located in the base of the hair's follicles slow, and eventually stop producing pigment. In some cases, gray hair may be caused by thyroid deficiencies, Waardenburg syndrome or a vitamin B 12 deficiency. Gray hair color typically occurs naturally as people age (see aging or achromotrichia below). The clear hairs appear as gray or white because of the way light is reflected from the hairs. Gray or white hair is not caused by a true gray or white pigment, but is due to a lack of pigmentation and melanin. For the fictional character, see Whitehair. For the Native American leader, see White Hair. Natural hair color can be black, brown, red and blond. Blond hair results from small amounts of brown eumelanin with no black eumelanin. If there is no black eumelanin, the result is strawberry blond.
Pheomelanin is generally found in elevated concentrations in blond and red hair, representing about one-third of total melanin content. Over 95% of melanin content in black and brown hair is eumelanin. All human hair has some amount of both pigments. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color more black eumelanin leads to blacker hair, and more brown eumelanin to browner hair. UV radiation most commonly comes from the sun, and thus populations from places closer to the equator tend to have darker hair, because eumelanin is generally more photoprotective than pheomelanin. Ultraviolet radiation (UV radiation) triggers greater synthesis of several compounds, including pro-opiomelanocortin (POMC), α-MSH, and ACTH, the result being increased eumelanin production. In addition, other genetic and environmental factors can affect hair color in humans for instance, mutations in the melanocortin 1 receptor (MC1R) gene can lead to red or auburn hair, and exposure to ultraviolet radiation can damage hair and alter its pigmentation.
ĭifferent hair color phenotypes arise primarily as a result of varying ratios of these two pigments in the human population, although Europeans show the greatest range in pigmentation overall. Inside the melanocytes, tyrosine is converted into L-DOPA and then L-dopaquinone, which in turn is formed into pheomelanin or eumelanin. Two types of pigment give hair its color, black-brown eumelanin and reddish-brown/reddish-yellow pheomelanin, synthesized by melanocytes. identified 13 DNA variations across 11 different genes that could be used to predict hair color. Regulatory DNA is believed to be closely involved in pigmentation in humans in general, and a 2011 study by Branicki et al.
Hair colors full#
The full genetic basis of hair color is complex and not fully understood. See also: Human genetic variation and Race and genetics straight dark hair amongst East Asians and Southeast Asians, a large variety of dark, fair, curly, straight, wavy and bushy hair amongst Europeans, West Asians and North Africans, curly, dark, and uniquely helical hair with Sub Saharan Africans, whilst gray, white or "silver" hair is often associated with age and wisdom. Some hair colors are associated with some ethnic groups due to observed higher frequency of particular hair color within their geographical region, e.g. Levels of melanin can vary over time causing a person's hair color to change, and it is possible to have hair follicles of more than one color on the same person. The tone of the hair is dependent on the ratio of black or brown eumelanin to yellow or red pheomelanin. Generally, if more melanin is present, the color of the hair is darker if less melanin is present, the hair is lighter. Human hair color is the pigmentation of human hair follicles due to two types of melanin: eumelanin and pheomelanin. A variety of human hair colors from top left, clockwise: black, brown, blonde, white, red
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