Hair color is hair follicle pigmentation due to two types of melanin: eumelanin and pheomelanin. Generally, if more eumelanin is present, the hair color is darker; if less eumelanin is present, hair is lighter. The darker the color of a person's natural hair, the more hair follicles they have on their scalp. The level of melanin may vary over time causing one's hair color to change, and it is possible to have more hair follicles of one color in the same person. Special hair color is associated with ethnic groups. Gray or white hair is associated with age.
The Fischer-Saller scale, named after Eugen Fischer and Karl Saller, is used in physical anthropology and medicine to determine hair color. This scale uses the following names: A (very light blonde), B to E (light blonde), F to L (blonde), M to O (dark blond), P to T (brown to brown), U to Y ( dark brown/black) and Roman numerals I to IV (red) and V to VI (red blond).
Video Human hair color
Genetics and hair color biochemistry
Two types of pigments give color to hair: eumelanin and pheomelanin. Pheomelanin orange and red hair color. All humans have some pheomelanin in their hair. Eumelanin, which has two subtypes of black or brown, determines the darkness of hair color. Low concentrations of eumelanin chocolate produce blond hair, while higher concentrations of eumelanin chocolate produce brown hair. Large amounts of black eumelanin produce black hair, while low concentrations produce white hair.
Pheomelanin is more bio-chemically stable than black eumelanin, but less bio-chemical than brown eumelanin, so it decomposes faster when oxidized. This is why bleach gives darker color to darker hair during artificial coloring process. As pheomelanin continues to degenerate, the hair will gradually become red, then orange, then yellow, and eventually become white.
The genetics of hair color are not yet established. According to one theory, at least two gene pairs control the color of a human hair.
One phenotype (brown/blonde) has a dominant chocolate allele and a recessive blonde allele. Someone with a chocolate allele will have brown hair; someone without a brown allele will be blonde. This explains why two brown-haired parents can produce blond children. However, this is only possible if both parents are heterozygous in hair color - meaning that both have one dominant brown hair allele and a recessive allele for blond hair, but as a dominant feature that masks a recessive person, the parents both have brown hair. Possible traits that may appear in offspring can be determined by Punnett square.
The other gene pair is a non-red/red pair, where the non-red allele (which suppresses pheomelanin production) is dominant and the red hair allele is recessive. A person with two copies of a red haired allele will have red hair.
The two-gene model does not explain all possible colors of brown, blonde, or red (eg, platinum blonde versus blonde/dark brown), nor does it explain why hair color is sometimes dark as a person's age. Some gene pairs control the light versus dark hair color in cumulative effects. A person's genotype for multifactorial properties can interact with the environment to produce a varied phenotype (see locus of quantitative properties).
Maps Human hair color
Natural hair color
Warna rambut alami bisa hitam, pirang, coklat, merah, atau putih; semua warna rambut alami termasuk abu-abu, putih dan pirang terang, adalah nuansa coklat.
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Rambut hitam
Black hair is the darkest hair color. It has a large amount of eumelanin and is less dense than other hair colors.
Brown hair
Brown hair is characterized by higher eumelanin levels and lower pheomelanin levels. Of the two types of eumelanin (black and brown), brown-haired people have brown eumelanin; they also usually have thick-medium hair strands. Brown-haired girls or women are often known as brunette.
Hair Chestnut is a hair color that is a reddish brown hair color. In contrast to reddish hair, reddish reddish color is darker. Hair chestnut is common among natives of Northern, Central, Western and Eastern Europe.
Blonde hair
Blond hair (or blond for women) ranges from almost white (platinum blond, long haired) to a dark golden blonde. Blonde blondes, blond and red blond hair, are the rarer species that contain the most pheomelanin. Dark Brown Hair With Light Brown Highlight Blond hair can have almost all proportions of pheomelanin and eumelanin, but it only has a small amount of both. More pheomelanin creates more golden blondes or strawberries, and more eumelanin creates sandy gray ash or color. Many children born with blond hair develop darker hair as they age, with the majority of natural blonds developing dark blonde hair color as they reach middle age. Pregnancy hormones speed up this process. Light blond hair is naturally rare in adulthood, with world population claims ranging from 2% natural blonds to 16% in the US. Blond hair is most commonly found in Northern and Western Europe and their offspring but can be found scattered throughout much of Europe. Studies in 2012 show that Melanesia's natural blond hair is caused by a recessive mutation in the tyrosinase-related protein 1 (TYRP1). In the Solomon Islands, 26% of the population carries genes; However, it does not exist outside of Oceania.
Blonde hair
Auburn's hair revolves around the spectrum of light to a dark red-brown color. The chemicals that cause redness are eumelanin (brown) and pheomelanin (red), with a higher proportion of red pheomelanin than those found in average brown hair. It is most commonly found in individuals of North and West European descent.
Red hair
Red hair ranges from blond strawberry blonde to brass, copper and red. This is due to variations in the Mc1r genes and is recessive. Red hair has the highest amount of pheomelanin, about 67%, and usually low eumelanin levels. In 1-2% of the population, this is the most unusual hair color in the world. This is most prominent found in the British Isles. Scotland has the highest proportion of redheads; 13 percent of the population has red hair and about 40 percent carry recessive redhead genes.
Gray and white hair
Gray or white hair - sometimes colloquially called "salt and pepper" when it is 'peppered' throughout dark hair - not caused by actual white or gray pigment, but because lack of pigmentation and melanin. The clear hair looks gray or white because of the light reflected from the hair. Gray hair color usually occurs naturally with age (see Aging or achromotrichia below). For some people this can happen at a very young age, even as young as 10 years.
In some cases, gray hair can be caused by a lack of thyroid, Waardenburg syndrome or vitamin B deficiency 12 . At some point in the life cycle of humans, the cells located at the base of the hair follicle are slow, and eventually stop producing pigments. Piebaldism is an autosomal dominant disorder of rare development of melanocytes, which can cause congenital white shells.
Europeans often start growing gray hairs in their mid 30s while Asians start graying in their 30s, but most Africans retain their original hair color until their mid-40s.
Gray is a gradual process; according to a study by L'Oreal, overall, of those aged between 45 and 65 years, 74% had gray hair, which accounted for an average of 27% of their heads, and about 1 in 10 people did not have gray hair -abu even after the age of 60.
Conditions affecting hair color
Penuaan atau achromotrichia
Children born with some hair color may find it gradually dark as they grow. Many blond, light brown, or red babies experience this. This is caused by genes that are muted and continued during childhood and puberty.
Hair color changes usually occur naturally as you get older, eventually turning your hair into gray and then white. This is called achromotrichia. Achromotrichia usually begins in the early to mid twenties in men and late twenties in women. More than 60 percent of Americans have gray hair at the age of 40. The graying age seems almost entirely due to genetics. Sometimes people are born with gray hair because they inherit that trait.
The order in which gray occurs usually: nose hair, head hair, beard, body hair, eyebrows.
In individuals who are not bald, hair can grow faster after changing color to gray.
Some genes seem to be responsible for graying. Bcl2 and Bcl -w are the first two to be found, then in 2016, the IRF4 gene (interferon regulatory factor 4) was announced after a study of 6,000 people living in five Latin States -USA. However, it was found that environmental factors controlled about 70% of graying hair cases.
Hair color changes occur when melanin stops are produced in hair roots and new hair grows without pigment. The stem cells at the base of the hair follicle produce melanocytes, the cells that produce and store pigments in the hair and skin. The death of melanocyte stem cells causes graying. It remains unclear why stem cells from one hair follicle may fail to activate more than a decade before they are in adjacent follicles less than a millimeter apart.
Gray hair may be triggered by the accumulation of hydrogen peroxide and very low levels of catalase enzyme, which breaks down hydrogen peroxide and relieves oxidative stress in patients suffering from vitiligo. Because vitiligo can cause the lashes to turn white, the same process is believed to be involved in hair on the head (and elsewhere) due to aging.
An imatinib anti-cancer drug has recently been shown to reverse the graying process. However, it is expensive and has potentially severe and deadly side effects, so it is not practically used to change the color of a person's hair. However, if the mechanism of imatinib action in melanocyte stem cells can be found, it is likely that a safer and cheaper substitute drug may one day be developed. It is not known whether imatinib has any effect on catalase, or if the reversal of the gray process is due to something else.
Stress
Anecdotes reported that stress, both chronic and acute, can cause achromotrichia earlier in the individual than it should be. Supporters show survivors, such as the survivors Harold Bride, or high-ranking politicians like Bill Clinton or Barack Obama. There is some evidence for chronic stress that causes premature achromotrichia, but no definite relationship has been established. It is well known that the stress hormone cortisol accumulates in human hair over time, but whether this has an effect on hair color has not been resolved.
Medical condition
Albinism is a genetic disorder in which little or no pigment is found in human hair, eyes, and skin. Her hair is often white or pale blond. However, it can be red, darker blonde, light brown, or sparse, even dark brown.
Vitiligo is the loss of hair and skin color that can occur as a result of auto-immune diseases. In the early 2013 study, the researchers treated the buildup of hydrogen peroxide that caused this by light-activated pseudo-catalase. This results in significant media coverage that further investigation may one day lead to a common non-dye treatment for gray hair.
Malnutrition is also known to cause hair to become lighter, thinner, and more fragile. Dark hair may turn redness or blonde due to decreased melanin production. This condition is reversible with proper nutrition.
Werner syndrome and pernicious anemia can also cause premature aging.
An uncontrolled study in 2005 showed that people aged 50-70 years with dark-colored eyebrows but gray hairs were significantly more likely to have type II diabetes than those who had eyebrows and gray hair.
Artificial Factors
A 1996 British Medical Journal study found that tobacco smoking can cause premature aging. Smokers were found four times more likely to start graying prematurely, compared with nonsmokers.
Gray hair may be temporarily dark after an inflammatory process, after electron-induced alopecia, and after several chemotherapy regimens. There is still much to be learned about human gray physiology.
There are no special diets, nutritional supplements, vitamins, or proteins that have been shown to slow, stop, or affect graying, though many have been marketed for years. However, French scientists who treated leukemia patients with new cancer drugs noted unexpected side effects: some of the patient's hair color was returned to pre-gray color.
Changes after death
The color of mummy hair or a buried body may change. Hair contains a mixture of black-brown-yellow eumelanin and red pheomelanin. Eumelanin is less chemically stable than pheomelanin and decomposes faster when oxidized. For this reason Egyptian mummies have reddish hair. Hair color changes faster under extreme conditions. It changes more slowly under dry oxidizing conditions (such as in funerals in sand or in ice) than under wet reduction conditions (such as wood burial or plaster coffins).
Hair coloring
Hair color can be changed by chemical process. Hair coloring is classified as "permanent" or "semi-permanent".
Permanent hair color means that the hair structure has been chemically altered until it is finally cut. This does not mean that synthetic colors will remain permanently. During the process, natural colors are removed, one or more colors, and synthetic colors have been put in place. All pigments come out of the cuticle. Natural colors stay longer and artificial will fade at the fastest (depending on the color molecule and pigment shape of the dye).
Permanent hair color gives the most flexibility because it can make hair lighter or darker and change the tone and color, but there are negative ones. Constant maintenance (monthly or six weekly) is very important to match new hair that grows throughout the hair, and to fade. A single color dye creates a flat and uniform color across the head, which can look unnatural and rough, especially in bright colors. To counter this, the modern trend is to use multiple colors - usually one color as a base with additional highlights or lowlights in other colors.
Semi permanent color washes over a period of time - usually four to six weeks, so root growth is less noticeable. The final color of each piece is affected by its original color and porosity, so there will be subtle color variations in the head - more natural and less rough than permanent dyes. However, this means gray and white hair will not color the same color as the rest of the head (in fact, some white hair will not absorb the color at all). Some gray and white hair will blend enough not to be seen, but as they become more widespread, there will be a point where semi-permanent alone will not be enough. Switch to 100% permanent color can be delayed using semi-permanent as the base color, with permanent highlight.
Semi permanent hair color can not lighten hair. Hair can only be lightened using a chemical lightener, such as bleach. Bleaching is always permanent because it eliminates natural pigments.
"Rinses" is a temporary hair color, usually applied to the hair during shampoo and washed again the next time the hair is washed.
See also
- The color of the human eye
- Human skin color
References
External links
- Media related to Human Hair color on Wikimedia Commons
Source of the article : Wikipedia
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