Human hair color
Human hair color is the pigmentation of
Genetics and biochemistry of hair color
The full genetic basis of hair color is complex and not fully understood.[1] Regulatory DNA is believed to be closely involved in pigmentation in humans in general,[2] and a 2011 study by Branicki et al. identified 13 DNA variations across 11 different genes that could be used to predict hair color.[3]
Two types of pigment give hair its color, black-brown
Different hair color
Pheomelanin colors hair
Natural hair colors
Blond | Dark blond | Medium brown | Dark brown | Reddish-brown | Red | Black | Gray | White |
Natural hair color can be black, brown, red and blonde.[10]
Color shade scale
The
Image gallery
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Natural black hair
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Dark brown hair
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Medium brown hair
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Light brown hair
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Chestnut brown hair
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Light chestnut brown hair
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Orange red hair
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Copper hair
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Strawberry blond hair
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Light blond hair
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Golden blond hair
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Medium blond hair
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Grey hair
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White hair
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White hair caused by albinism
Black hair
Black hair or jet black hair is the darkest hair color. It has large amounts of eumelanin and is more dense than other hair colours and is the commonly seen hair color in Asia and Africa due the fact that the people in these regions tend to have lower levels of tyrosinase in their bodies. Black eumelanin secretion causes the hair to turn black, which indicates that the MC1R is in the active state. Jet black hair, the darkest shade will not have a warm, neutral tone but a sheen which can seem almost blue, like the iridescence of a raven's wing; hence, sometimes referred to as raven-black. Jet black hair appears to have reflective silver color in bright sunlight.[12][13]
Brown hair
Brown hair is the second most common human hair color, after black. Brown hair is characterized by higher levels of eumelanin and lower levels of pheomelanin. Of the two types of eumelanin (black and brown), brown-haired people have brown eumelanin; they also usually have medium-thick strands of hair. Brown-haired girls or women of European, West Asian or North African descent are often known as brunettes.
Chestnut hair is a hair color which is a reddish shade of brown hair. In contrast to auburn hair, the reddish shade of chestnut is darker. Chestnut hair is common among the native peoples of Northern, Central, Western, and Eastern Europe and is also found in
Auburn hair
Auburn hair ranges along a spectrum of light to dark red-brown shades. The chemicals which cause auburn hair are
Red hair
Red hair ranges from light strawberry blond shades to
Blond hair
Blond (sometimes blonde for women) hair ranges from pale white (platinum blond) to dark gold blond. Strawberry blond, a mixture of blond and red hair, is a much rarer type containing the most
Gray and white hair
Gray or white hair is not caused by a true gray or white pigment, but is due to a lack of pigmentation and melanin. The clear hairs appear as gray or white because of the way light is reflected from the hairs. Gray hair color typically occurs naturally as people age (see aging or achromotrichia below).
Conditions affecting hair color
Aging or achromotrichia
Children born with some hair colors may find it gradually darkens as they grow. Many blond, light brown, or red haired infants experience this. This is caused by genes being turned on and off during early childhood and puberty.[20]
Changes in hair color typically occur naturally as people age, eventually turning the hair gray and then white. This is called achromotrichia. Achromotrichia normally begins in the early to mid-twenties in men and late twenties in women. More than 60 percent of Americans have some gray hair by age 40. The age at which graying begins seems almost entirely due to genetics. Sometimes people are born with gray hair because they inherit the trait.[21]
The order in which graying happens is usually: nose hair, hair on the head, beard, body hair, eyebrows.[22]
Hair coloring
Hair color can be changed by a chemical process. Hair coloring is classed as "permanent" or "semi-permanent".
Permanent hair color means that the hair's structure has been chemically altered until it is eventually cut away. This does not mean that the synthetic color will remain permanently. During the process, the natural color is removed, one or more shades, and synthetic color has been put in its place. All pigments wash out of the cuticle. Natural color stays in much longer and artificial will fade the fastest (depending on the color molecules and the form of the dye pigments).
Permanent hair color gives the most flexibility because it can make hair lighter or darker as well as changing tone and color, but there are negatives. Constant (monthly or six-weekly) maintenance is essential to match new hair growing in to the rest of the hair, and to remedy fading. A one-color permanent dye creates a flat, uniform color across the whole head, which can look unnatural and harsh, especially in a fair shade. To combat this, the modern trend is to use multiple colors—usually one color as a base with added highlights or lowlights in other shades.
Semi-permanent color washes out over a period of time—typically four to six weeks, so root regrowth is less noticeable. The final color of each strand is affected by its original color and porosity, so there will be subtle variations in color across the head—more natural and less harsh than a permanent dye. However, this means that gray and white hair will not dye to the same color as the rest of the head (in fact, some white hair will not absorb the color at all). A few gray and white hairs will blend in sufficiently not to be noticeable, but as they become more widespread, there will come a point where a semi-permanent alone will not be enough. The move to 100% permanent color can be delayed by using a semi-permanent as a base color, with permanent highlights.
Semi-permanent hair color cannot lighten hair.[23] Hair can only be lightened using chemical lighteners, such as bleach. Bleaching is always permanent because it removes the natural pigment.
"Rinses" are a form of temporary hair color, usually applied to hair during a shampoo and washed out again the next time the hair is washed.
See also
References
- ^ Genetics Home Reference. "Is hair color determined by genetics?". US National Library of Medicine. Retrieved May 10, 2020.
- ^ Pennisi, Elizabeth (June 1, 2014). "The Genetics of Blond Hair". Science Magazine. Retrieved May 10, 2020.
- PMID 21197618.
- ^ ISBN 978-3-642-64547-1.
- ^ PMID 30607038.
- ^ PMID 29083759. Retrieved May 22, 2020.
- PMID 19297406.
- PMID 15157906.
- ^ ISBN 9783642256103. Retrieved May 22, 2020.
- ^ "Is hair color determined by genetics?: MedlinePlus Genetics". medlineplus.gov. Retrieved April 12, 2023.
- ^ "Change in Hair Pigmentation in Children from Birth to 5 Years in a European Population (Longitudinal Study)". Forensic Science Communications. Archived from the original on March 20, 2014. Retrieved March 19, 2014.
- S2CID 5121042.
- ^ "Genetics of Hair Color". Medical News. December 29, 2022.
- ^ "Scientists question whether rare reds are headed for extinction". Azcentral.com. May 5, 2005. Archived from the original on May 11, 2023. Retrieved April 3, 2012.
- ^ "The Genetics of Red Hair: What Causes Natural Red Hair?". Brighthub.com. September 4, 2009. Retrieved April 3, 2012.
- ^ "Michigan twins featured in book about rare red hair". MLive.com. November 3, 2009. Retrieved April 3, 2012.
- PMID 22556244.
- ^ Alice Klein (June 6, 2020). "Grey hairs sometimes regain their colour when we feel less stressed". New Scientist.
- S2CID 218764733.
- ^ "Understanding Genetics: Human Health and the Genome". Archived from the original on July 24, 2011. Retrieved July 25, 2011.
- PMID 23974581.
- ^ 鼻毛にも白髪は生えるの? (in Japanese). Retrieved July 3, 2012.
- ISBN 9783319456959.