Hair color is the pigmentation of hair follicles due to two types of melanin, eumelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. Many melanins are insoluble salts and show affinity to water.[citation needed] The most common form of biological and pheomelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acid,. Generally, if more melanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole is present, the color of the hair is darker; if less melanin is present, the hair is lighter. 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.

Particular hair colors can be associated with ethnic groups - however, due to migration and global travel, considerable variations have developed in the hair color of individuals within an ethnic group, creating a greatly increased diversity of hair color.

Genetics and biochemistry of hair color

Two types of pigment give hair its color: eumelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. Many melanins are insoluble salts and show affinity to water.[citation needed] The most common form of biological and pheomelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acid,. Pheomelanin colors hair red The word red comes from the Old English rēad. Further back, the word can be traced to the Proto-Germanic rauthaz and the Proto-Indo European root reudh-. In Sanskrit, the word rudhira means red or blood. In the English language, the word red is associated with the color of blood, certain flowers , and ripe fruits (e.g. apples, cherries). Fire is. Eumelanin, which has two subtypes of black Black is the color of objects that do not emit or reflect light in any part of the visible spectrum; they absorb all such frequencies of light. Although black is sometimes described as an "achromatic", or hueless, color, in practice it can be considered a color, as in expressions like "black cat" or "black paint" or brown Brown is a color term, denoting a range of composite colors produced by a mixture of orange, red, rose, or yellow with black or gray. The term is from Old English brún, in origin for any dusky or dark shade of color. The Common Germanic adjective *brûnoz, *brûnâ meant both dark colors and a glistening or shining quality, whence burnish. The, determines the darkness of the hair color. A low concentration of brown eumelanin results in blond hair, whereas a higher concentration of brown eumelanin will color the hair brown. High amounts of black eumelanin result in black hair, while low concentrations give gray hair. All humans have some pheomelanin in their hair.

Pheomelanin is more chemically stable than black eumelanin, but less chemically stable than brown eumelanin, so it breaks down more slowly when oxidized Redox describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. This can be either a simple redox process, such as the oxidation of carbon to yield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of sugar(C6H12O6) in the. This is why bleach A bleach is a chemical that removes colors or whitens, often via oxidation. Common chemical bleaches include household chlorine bleach, a solution of approximately 3–6% sodium hypochlorite , and oxygen bleach, which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate, sodium percarbonate, sodium persulfate, gives darker hair a reddish tinge during the artificial coloring process. As the pheomelanin continues to break down, the hair will gradually become orange, then yellow, and finally white.

The genetics of hair colors are not yet firmly established. According to one theory, at least two gene pairs control human hair color.

One phenotype (brown/blond) has a dominant brown allele An allele (pronounced /ˈæliːl/ , /əˈliːl/ (US); from the Greek αλληλος allelos, meaning each other) is one of two or more forms of the DNA sequence of a particular gene and a recessive blond allele. A person with a brown allele will have brown hair; a person with no brown alleles will be blond. This explains why two brown-haired parents can produce a blond-haired child.

The other gene pair is a non-red/red pair, where the not-red allele (which suppresses production of pheomelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acid,) is dominant and the allele for red hair is recessive. A person with two copies of the red-haired allele will have red hair, but it will be either auburn or bright reddish orange depending on whether the first gene pair gives brown or blond hair, respectively.

The two-gene model does not account for all possible shades of brown, blond, or red (for example, platinum blond versus dark blonde/light brown), nor does it explain why hair color sometimes darkens as a person ages. Several gene pairs control the light versus dark hair color in a cumulative effect. A person's genotype for a multifactorial trait can interact with environment to produce varying phenotypes (see quantitative trait locus Inheritance of quantitative traits or polygenic inheritance refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to the interactions between two or more genes and their environment. Though not necessarily genes themselves, quantitative trait loci are stretches of DNA that are closely linked to the).

Natural hair colors

Natural hair color can be black, brown, blond, or red, depending on a person's ethnic origins. Hair color is typically genetically associated with certain skin tones and eye colors.

Brown hair

Brown hair is the most common in Southern and Eastern Europe and most of the Southern United States and some other parts of the world. It 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 people are also known as brunettes Brown hair varies from light brown to almost black hair. It is characterized by higher levels of the dark pigment eumelanin and lower levels of the pale pigment phaeomelanin. Its strands are thicker than those of fair hair but not as much as those of red hair. People with brown hair are often referred to as brunettes, the feminine form, and/brunets.

Black hair

Black hair is the darkest hair color and is the most common. It has large amounts of eumelanin and is less dense than other hair colors. It can range from soft black to blue-black or jet-black hair. It is also the shiniest of all hair colors.^[1]

Blond hair

Blond hair ranges from nearly white (platinum blonde, tow-haired) to a dark golden blond. Strawberry blond, a mixture of blond and red hair is a much rarer type containing the most amounts of pheomelanin.

Blond hair can have almost any proportion of pheomelanin and eumelanin, but both only in small amounts. More pheomelanin creates a more golden blond color, and more eumelanin creates an ash blond. Blond hair is common in people with European descent, but rare among people of non-European origin. Many children born with blond hair develop darker hair as they age. Blond hair is most commonly found in Northern Europeans, and their descendants and in the Northern United States.

Auburn hair

Auburn hair ranges from light to reddish brown. The chemicals which cause auburn hair are eumelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. Many melanins are insoluble salts and show affinity to water.[citation needed] The most common form of biological (brown) and pheomelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acid,. It is most commonly found in individuals of Northern and Western Europe decent, particularly France.

Chestnut hair

Chestnut hair is like auburn hair, but chestnut hair has a darker reddish shade of brown hair than auburn. It is most commonly found in individuals of Eastern European descent.

Red hair

Red hair ranges from vivid strawberry shades to deep auburn and burgundy. It is caused by a variation in the Mc1r The melanocortin 1 receptor , also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein-coupled receptor which binds to a class of pituitary peptide hormones known as the melanocortins, of which include adrenocorticotropic hormone (ACTH) and the different forms of gene and believed to be recessive Dominance in genetics is a relationship between different forms of a gene at a particular physical location (locus) on a chromosome.^[2] Red hair has the highest amounts of pheomelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acid, and usually low levels of eumelanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. Many melanins are insoluble salts and show affinity to water.[citation needed] The most common form of biological, and is the least common hair color in the world while the most prominent is found in Scotland and Ireland, along with Norway, Denmark, Sweden, and The Netherlands. ^[3][4][5]

Grey and white hair

Grey or White hair is not actually a true Grey or White pigment. In fact, it is clear due to lack of pigmentation and melanin. The clear hairs are seen as Grey or White because of the way light hits it. Grey hair color typically occurs naturally as people age Ageing or aging (American and Canadian English) is the accumulation of changes in an organism or object over time. Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline. Reaction time, for example, may slow with age, while (see "Effects of aging on hair color", below). For some people this can happen at a very young age (for example, at the age of 10). The same can be said for white hair. In some cases, grey hair may be caused by thyroid deficiencies or a deficiency of B₁₂ Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins. It is normally involved in the metabolism of every cell of the body, especially affecting DNA synthesis and.^[6]

The Journal of Investigative Dermatology published a study in 2005 that claimed white people will begin to gray in their mid-thirties and Asian people begin graying in their late thirties, but most black people can retain their original hair color until their mid-forties.^[7] People with albinism Albinism is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including humans. The most common term used for an may have white hair due to low amounts of melanin.

Conditions affecting hair color

Aging

Children born with some hair colors may find it gradually darkens as they grow. Many blond, strawberry blond, light brown, or red haired infants experience this.

Changes in hair color typically occur naturally as people age, eventually turning the hair gray and then white. This is called achromotrichia. More than 40 percent of Americans have some gray hair by age 40, but white hairs can appear as early as childhood. The age at which graying begins seems almost entirely due to genetics Genetics , a broad discipline of biology, is the science of heredity, genes, DNA, mutation, etc., and their functions and aspects in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. However, the modern science of. Sometimes people are born with gray hair because they inherit the trait.

Two genes A gene is a unit of heredity in a living organism. It is normally a stretch of DNA that codes for a type of protein or for an RNA chain that has a function in the organism. All living things depend on genes, as they specify all proteins and functional RNA chains. Genes hold the information to build and maintain an organism's cells and pass genetic appear to be responsible for the process of graying, Bcl2 and Bcl-w.^{[citation needed]} The change in hair color occurs when melanin Melanin (Greek μέλας, black; pronounced /ˈmɛlənɪn/ ) is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole ceases to be produced in the hair root and new hairs grow in without pigment. The stem cells Stem cells are cells found in all multi cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiate into a diverse range of specialized cell types. Research in the stem cell field grew out of findings by Canadian scientists Ernest A. McCulloch and James E. Till in the 1960s. The two at the base of hair follicles produce melanocytes Melanocytes (pronounced /mɛˈlænɵsaɪt/ ) are melanin-producing cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), the inner ear, meninges, bones, and heart. Melanin is a pigment which is primarily responsible for the color of skin, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of graying.^[8]

Sex

Human females are more likely to have lighter colored hair than males, whereas males are more likely to have black or dark hair. Red and blond hair are relatively more common in women than in men.^[9]

Medical conditions

Albinism Albinism is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including humans. The most common term used for an is a genetic abnormality in which little or no pigment is found in human hair, eyes or skin. The hair is often white or pale blond.

Vitiligo Vitiligo is a chronic disorder that causes depigmentation in patches of skin. It occurs when melanocytes, the cells responsible for skin pigmentation, die or are unable to function is a patchy loss of hair and skin color that may occur as the result of an auto-immune disease.

Malnutrition Malnutrition is the insufficient, excessive or imbalanced consumption of nutrients. A number of different nutrition disorders may arise, depending on which nutrients are under or overabundant in the diet is also known to cause hair to become lighter, thinner, and more brittle. Dark hair may turn reddish or blondish due to the decreased production of melanin. The condition is reversible with proper nutrition.

Werner syndrome and pernicious anemia Pernicious anemia is a form of megaloblastic anemia can also cause premature graying.

A recent study demonstrated that people 50–70 years of age with dark eyebrows but gray hair are significantly more likely to have type II diabetes Diabetes mellitus type 2 or type 2 diabetes (formerly called non -insulin-dependent diabetes mellitus , or adult-onset diabetes) is a disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency. Diabetes is often initially managed by increasing exercise and dietary modification. As the than those with both gray eyebrows and hair.^[10]

Artificial factors

A 1996 British Medical Journal BMJ is a partially open access medical journal. It is among the most influential and widely read peer-reviewed general scientific journals in the field of medicine in the world study conducted by J.G. Mosley, MD found that tobacco smoking Tobacco smoking is the practice where tobacco is burned and the vapors either tasted or inhaled. The practice began as early as 5000–3000 BC. Many civilizations burnt incense during religious rituals, which was later adopted for pleasure or as a social tool. Tobacco was introduced to the Old World in the late 1500s where it followed common trade may cause premature graying. Smokers were found to be four times more likely to begin graying prematurely, compared to nonsmokers.^[11]

Gray Complementary colors are defined to mix to grey, either additively or subtractively, and many color models place complements opposite each-other in a color wheel. To produce grey in RGB displays, the R, G, and B primary light sources are combined in proportions equal to that of the white point. In four-color printing, greys are produced either by hair may temporarily darken after inflammatory processes, after electron-beam-induced alopecia, and after some chemotherapy regimens. Much remains to be learned about the physiology of human graying.^[12]

There are no special diets, nutritional supplements, vitamins, nor proteins that have been proven to slow, stop, or in any way affect the graying process, although many have been marketed over the years. However, French scientists treating leukemia Leukemia or leukaemia (Standard English; Greek leukos λευκός, "white"; aima αίμα, "blood") is a cancer of the blood or bone marrow characterized by an abnormal increase of blood cells, usually leukocytes (white blood cells). Leukemia is a broad term covering a spectrum of diseases. In turn, it is part of the even patients with a new cancer drug noted an unexpected side effect: some of the patients' hair color was restored to their pre-gray color.^[13]

Changes after death

The hair color of mummies A mummy is a corpse whose skin and organs have been preserved by either intentional or incidental exposure to chemicals, extreme coldness, very low humidity, or lack of air when bodies are submerged in bogs. Presently, the oldest discovered mummified human corpse was a decapitated head dated as 6,000 years old and was found in 1936. The most or buried bodies can change. Hair contains a mixture of black-brown-yellow eumelanin and red pheomelanin. Eumelanin is less chemically stable than pheomelanin and breaks down faster when oxidized. It is for this reason that Egyptian mummies have reddish hair. The color of hair changes faster under extreme conditions. It changes more slowly under dry oxidizing conditions (such as in burials Burial , also called interment and inhumation, is the act of placing a person or object into the ground. This is accomplished by excavating a pit or trench, placing an object in it, and covering it over in sand or in ice) than under wet reducing conditions (such as burials in wood or plaster coffins).^[14]

Hair coloring

Hair color can be changed by a chemical process. Hair coloring is classed as "permanent" or "semi-permanent".

Permanent color, as the name suggests, permanently colors the hair - however because hair is constantly growing, the color will eventually grow out as new, uncolored hair grows in.

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 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 dark 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. 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

• Eye color Eye color is a polygenic phenotypic character and is determined by the amount and type of pigments in the eye's iris. Humans and animals have many phenotypic variations in eye color, as blue, brown, gray, green and others. These variations constitute phenotypic traits
• Human skin color
• List of Mendelian traits in humans

Notes

1. ^ . Black hair is common is almost all world continent, and most second and third world countries have black hair as the dominant hair color. "Hair Color:Two Hair Colors for an Infinite Pallette". http://www.hair-science.com/_int/_en/topic/topic_sousrub.aspx?tc=ROOT-HAIR-SCIENCE%5EAMAZINGLY-NATURAL%5ECOLOR-PALETTE&cur=COLOR-PALETTE. Retrieved 2010-02-27.
2. ^ In males, the supposedly recessive trait is often expressed in parts of the facial hair or beard. Valverde P, Healy E, Jackson I, Rees JL, Thody AJ (November 1995). "Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans". Nat. Genet. 11 (3): 328–30. doi:10.1038/ng1195-32810.1038/ng1195-328. PMID 7581459.
3. ^ http://www.azcentral.com/ent/pop/articles/0505redhair05.html
4. ^ http://www.brighthub.com/science/genetics/articles/4704.aspx
5. ^ http://www.mlive.com/entertainment/index.ssf/2009/11/michigan_twins_featured_in_boo.html
6. ^ Juangbhanit C, Nitidanhaprabhas P, Sirimachan S, Areekul S, Tanphaichitr VS (June 1991). "Vitamin B₁₂ deficiency: report of a childhood case". J Med Assoc Thai 74 (6): 348–54. PMID 1744541.
7. ^ Burford, Michelle (August 2009). "Gray Hair Myths and Facts". AOL Health. http://www.aolhealth.com/healthy-living/beauty-skin-care/gray-hair. Retrieved August 2009.
8. ^ Nishimura EK, Granter SR, Fisher DE. Mechanisms of hair graying: Incomplete melanocyte stem cell maintenance in the niche.
9. ^ Duffy DL, Montgomery GW, Chen W, et al. (February 2007). "A three-single-nucleotide polymorphism haplotype in intron 1 of OCA2 explains most human eye-color variation". Am. J. Hum. Genet. 80 (2): 241–52. doi:10.1086/510885. PMID 17236130.
10. ^ Department of Dermatology, Academic Teaching Hospital Dresden-Friedrichstadt (2005 December;14). "Eyebrow color in diabetics". Acta Dermatovenerol Alp Panonica Adriat. 14 (4): 157–60. PMID 16435045.
11. ^ Mosley JG, Gibbs AC (1996). "Premature grey hair and hair loss among smokers: a new opportunity for health education?". BMJ 313 (7072): 1616. PMID 8991008. PMC 2359122. http://bmj.bmjjournals.com/cgi/content/full/313/7072/1616.
12. ^ Cline DJ (April 1988). "Changes in hair color". Dermatol Clin 6 (2): 295–303. PMID 3288386.
13. ^ Cancer drug restores hair color BBC News
14. ^ Interactive Dig Hierakonpolis - Archaeological Hair

External links

• A chart of hair colors
• A chart of popular hair colors along with their representative names

Categories: Hair color

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• Color Preferences: Encyclopedia

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