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Human hair color is the pigmentation of human
hair follicle The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between h ...
s due to two types of
melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
:
eumelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amin ...
and
pheomelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the am ...
. Generally, if more melanin is present, the color of the hair is darker; if less melanin is present, the hair is lighter. The tone of the hair is dependent on the ratio of black or brown eumelanin to yellow or red pheomelanin. 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. Some hair colors are associated with some ethnic groups due to observed higher frequency of particular hair color within their geographical region, e.g. straight dark hair amongst East Asians, a large variety of dark, fair, curly, wavy and bushy hair amongst Europeans, curly, dark, and uniquely helical hair with Africans, whilst gray, white or "silver" hair is often associated with
age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...
and wisdom.


Genetics and biochemistry of hair color

The full genetic basis of hair color is complex and not fully understood. Regulatory DNA is believed to be closely involved in pigmentation in humans in general, and a 2011 study by Branicki et al. identified 13 DNA variations across 11 different genes that could be used to predict hair color. Two types of pigment give hair its color, black-brown
eumelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amin ...
and reddish-brown/reddish-yellow
pheomelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the am ...
, synthesized by
melanocytes Melanocytes are melanin-producing neural crest-derived 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, vaginal epithelium, meninges, bones, and heart. Mel ...
. Inside the melanocytes, tyrosine is converted into L-DOPA and then
L-dopaquinone -Dopaquinone also known as ''o''-dopaquinone is a metabolite of L-DOPA (L-dihydroxyphenylalanine) and a precursor of melanin. Biosynthesis of melanin occurs in melanocytes, where tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyph ...
, which in turn is formed into pheomelanin or eumelanin. Different 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. 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. Ultraviolet radiation (UV radiation) triggers greater synthesis of several compounds, including
pro-opiomelanocortin Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is synthesized in corticotrophs of the anterior pituitary from the 267-amino-acid-long polypeptide precursor pre-pro-opiomelanocortin (pre-POMC), by the ...
(POMC),
α-MSH α-Melanocyte-stimulating hormone (α-MSH) is an endogenous peptide hormone and neuropeptide of the melanocortin family, with a tridecapeptide structure and the amino acid sequence Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2. It ...
, and
ACTH Adrenocorticotropic hormone (ACTH; also adrenocorticotropin, corticotropin) is a polypeptide tropic hormone produced by and secreted by the anterior pituitary gland. It is also used as a medication and diagnostic agent. ACTH is an important co ...
, the result being increased eumelanin production. 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. Pheomelanin colors hair
orange Orange most often refers to: *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Orange (colour), from the color of an orange, occurs between red and yellow in the visible spectrum * ...
and
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...
. Eumelanin, which has two subtypes of
black Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have of ...
or
brown Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing or painting, brown is usually made by combining the colors orange and black. In the RGB color model used ...
, determines the darkness of the hair color; more black eumelanin leads to blacker hair, and more brown eumelanin to browner hair. All human hair has some amount of both pigments. Over 95% of melanin content in black and brown hair is eumelanin. Pheomelanin is generally found in elevated concentrations in blond and red hair, representing about one-third of total melanin content. If there is no black eumelanin, the result is strawberry blond. Blond hair results from small amounts of brown eumelanin with no black eumelanin.


Natural hair colors

Natural hair color can be black, brown, red, blond, or white.


Color shade scale

The Fischer–Saller scale, named after Eugen Fischer and , is used in
physical anthropology Biological anthropology, also known as physical anthropology, is a scientific discipline concerned with the biological and behavioral aspects of human beings, their extinct hominin ancestors, and related non-human primates, particularly from an e ...
and medicine to determine the shades of hair color. The scale uses the following designations: A (very light blond), B to E (light blond), F to L (
blond Blond (male) or blonde (female), also referred to as fair hair, is a hair color characterized by low levels of the dark pigment eumelanin. The resultant visible hue depends on various factors, but always has some yellowish color. The color can ...
), M to O (dark blond), P to T ( light brown to brown), U to Y (dark brown to
black Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have of ...
) and Roman numerals I to IV (
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...
) and V to VI (red blond).


Image gallery

File:Woman with mid-back length black hair from behind 01.jpg,
Black hair Black hair is the darkest and most common of all human hair colors globally, due to larger populations with this dominant trait. It is a dominant genetic trait, and it is found in people of all backgrounds and ethnicities. Black hair contains ...
File:Chinese American girl.jpg, Natural black hair File:Short brown hair.jpg, Dark brown hair File:Young man with short brown hair from behind (1 October 2022) 05 (cropped).jpg, Medium brown hair File:Little girl with brown hair.jpg, Natural brown hair File:Goofy Boy.jpg, Light brown hair File:Yvonne Catterfeld.jpg, Chestnut brown hair File:A child of chappargram.JPG, Light chestnut brown hair File:Rotschopf.jpg, Auburn hair File:Rupert Grint.jpg, Red hair File:German Woman Portrait - Dutch summer festival of the Redhead Day in Breda, September 2010.jpg, Orange red hair File:נערה ג'ינג'ית.JPG, Copper hair File:Elena Kazantseva 00.jpg,
Titian hair Titian is a tint of red hair, most commonly described as brownish- orange in color. It is often confused with Venetian and auburn. Etymology The term originates from Titian, an Italian painter who would often depict women with red hair of this ...
File:Strawberry Blond Girl.jpg, Strawberry blond hair File:Lucy Merriam.jpg, Light blond hair File:Goldenblonde.JPG, Golden blond hair File:TKvamme.jpg, Medium blond hair File:Kofi Annan.jpg, Grey hair File:Rapolder uwe 600.jpg, White hair File:Albinisitic man portrait.jpg, White hair caused by
albinism Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino. Varied use and interpretation of the term ...


Black hair

Black hair is the darkest hair color. It has large amounts of eumelanin and is more dense than other hair colors.


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 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.


Auburn hair

Auburn hair ranges along a spectrum of light to dark red-brown shades. The chemicals which cause auburn hair are
eumelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amin ...
(brown) and
pheomelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the am ...
(red), with a higher proportion of red-causing pheomelanin than is found in average brown hair. It is most commonly found in individuals of Northern and Western European descent. It can also be the result of a mutation in the melanocortin 1 receptor gene.


Red hair

Red hair ranges from light strawberry blond shades to titian, copper, and completely red. Red hair has the highest amounts of
pheomelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the am ...
, around 67%, and usually low levels of
eumelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amin ...
. At 1–2% of the west Eurasian population, it is the least common hair color in the world. It is most prominently found in the
British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...
and in
Udmurtia Udmurtia (russian: Удму́ртия, r=Udmúrtiya, p=ʊˈdmurtʲɪjə; udm, Удмуртия, ''Udmurtija''), or the Udmurt Republic (russian: Удмуртская Республика, udm, Удмурт Республика, Удмурт � ...
. Scotland has the highest proportion of redheads; 13 percent of the population has red hair and approximately 40 percent carry the recessive redhead gene.


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
pheomelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the am ...
. Blond hair can have almost any proportion of pheomelanin and
eumelanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amin ...
, but has only small amounts of both. More pheomelanin creates a more golden or strawberry blond color, and more eumelanin creates an ash or sandy blond color. Blond hair is most commonly found in Northern and Northeastern Europeans and their descendants but can be found spread around most of Europe. Studies in 2012 showed that naturally blond hair of Melanesians is caused by a recessive mutation in tyrosinase-related protein 1 (TYRP1). In the Solomon Islands, 26% of the population carry the gene; however, it is absent outside of Oceania.


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 Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...
(see aging or achromotrichia below). In some cases, gray hair may be caused by thyroid deficiencies,
Waardenburg syndrome Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or one blue eye and one brown eye), a white forelock ...
or a vitamin B12 deficiency. 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. Piebaldism is a rare
autosomal dominant In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...
disorder of
melanocyte Melanocytes are melanin-producing neural crest-derived 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, vaginal epithelium, meninges, bones, and heart. M ...
development, which may cause a
congenital A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...
white forelock. Europeans 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. Permanently white hair starting in childhood can be genetically inherited, but unlike
albinism Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino. Varied use and interpretation of the term ...
, there are no negative medical implications. The trait follows X-linked recessive inheritance, and so is more common in men, and women can be carriers without being affected. Graying is a gradual process; according to a study by L'Oreal, overall, of those between 45 and 65 years old, 74% had some gray hair, covering an average of 27% of their head, and approximately 1 in 10 people had no gray hairs even after the age of 60.
Marie Antoinette syndrome Canities subita, also called Marie Antoinette syndrome or Thomas More syndrome, is an alleged condition of hair turning white overnight due to stress or trauma. The trivial names come from specific cases in history including that of Queen Marie An ...
is a proposed phenomenon in which sudden whitening is caused by stress. It has been found that some hairs can become colored again when stress is reduced.


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. 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. The order in which graying happens is usually: nose hair, hair on the head, beard, body hair, eyebrows. In non-balding individuals, hair may grow faster once it turns gray. Unlike in the skin where pigment production is continuous,
melanogenesis Melanocytes are melanin-producing neural crest-derived 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, vaginal epithelium, meninges, bones, and heart. Mela ...
in the hair is closely associated with stages of the hair cycle. Hair is actively pigmented in the
anagen The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between h ...
phase and is "turned off" during the
catagen The growth of human hair occurs everywhere on the body except for the soles of the feet, the inside of the mouth, the lips, the backs of the ears, the palms of the hands, some external genital areas, the navel, scar tissue, and, apart from eyelas ...
phase, and absent during telogen. Thus, a single hair cannot be white on the root side, and colored on the terminal side. Several genes appear to be responsible for the process of graying. ''Bcl2'' and ''Bcl-w'' were the first two discovered, then in 2016, the
IRF4 Interferon regulatory factor 4 (IRF4) also known as ''MUM1'' is a protein that in humans is encoded by the ''IRF4'' gene, located at 6p25-p23. IRF4 functions as a key regulatory transcription factor in the development of human immune cells.Nam S, ...
(interferon regulatory factor 4) gene was announced after a study of 6,000 people living in five Latin American countries. However, it found that environmental factors controlled about 70% of cases of hair graying. The change in hair color occurs when melanin ceases to be produced in the hair root and new hairs grow in without pigment. The
stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of ...
s at the base of
hair follicle The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction between h ...
s produce
melanocyte Melanocytes are melanin-producing neural crest-derived 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, vaginal epithelium, meninges, bones, and heart. M ...
s, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of graying. It remains unclear why the stem cells of one hair follicle may fail to activate well over a decade before those in adjacent follicles less than a millimeter apart. Vitamins and minerals that are known to slow down the graying process are vitamin B-12, C, D, H (Biotin), and the mineral iron. Also, an abnormal
pituitary gland In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The hypoph ...
or thyroid gland can cause hair to turn gray. Graying of hair may be triggered by the accumulation of hydrogen peroxide and abnormally low levels of the enzyme
catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...
, which breaks down hydrogen peroxide and relieves oxidative stress in patients with vitiligo. Since vitiligo can cause eyelashes to turn white, the same process is believed to be involved in hair on the head (and elsewhere) due to aging. The
anti-cancer drug Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...
imatinib Imatinib, sold under the brand names Gleevec and Glivec (both marketed worldwide by Novartis) among others, is an oral chemotherapy medication used to treat cancer. Imatinib is a small molecule inhibitor targeting multiple receptor tyrosine kin ...
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 practical to use to alter a person's hair color. Nevertheless, if the
mechanism of action In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targ ...
of imatinib on melanocyte stem cells can be discovered, it is possible that a safer and less expensive substitute drug might someday be developed. It is not yet known whether imatinib has an effect on catalase, or if its reversal of the graying process is due to something else.


Stress

Anecdotes report that stress, both chronic and acute, may induce achromotrichia earlier in individuals than it otherwise would have. Proponents point to survivors of disasters, such as ''Titanic'' survivor
Harold Bride Harold Sydney Bride (11 January 1890 – 29 April 1956) was a British merchant seaman and the junior wireless officer on the ocean liner RMS ''Titanic'' during its ill-fated maiden voyage. After the ''Titanic'' struck an iceberg at 11:40 pm ...
, prisoner of war John McCain, or high-level politicians such as Bill Clinton or
Barack Obama Barack Hussein Obama II ( ; born August 4, 1961) is an American politician who served as the 44th president of the United States from 2009 to 2017. A member of the Democratic Party, Obama was the first African-American president of the U ...
. There is some evidence for chronic stress causing premature achromotrichia, but no definite link has been established. It is known that the stress hormone ''
cortisol Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone. It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland ...
'' accumulates in human hair over time, but whether this has any effect on hair color has not yet been resolved. A 2020 paper, published in the journal ''Nature'' reported that stress can cause hair to lose its pigment. An overactive immune response can destroy melanocytes and melanocyte stem cells in black-haired rats. When intentionally subjecting them to panic, they bleached their coat. The next time the rats' coat grew, there were no melanocyte stem cells in these damaged follicles, so white hairs sprouted, and the color loss was permanent.


UV damage

Excessive exposure to the sun is the most common cause of structural damage of the hair shaft. Photochemical hair damage encompasses hair protein degradation and loss, as well as hair pigment deterioration Photobleaching is common among people with European ancestry. Around 72 percent of customers who agreed to be involved in a study and have European ancestry reported in a recent
23andMe 23andMe Holding Co. is a publicly held personal genomics and biotechnology company based in South San Francisco, California. It is best known for providing a direct-to-consumer genetic testing service in which customers provide a saliva sample t ...
research that the sun lightens their hair. The company also have identified 48 genetic markers that may influence hair photobleaching.


Medical conditions

Albinism Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino. Varied use and interpretation of the term ...
is a genetic abnormality in which little or no pigment is found in human hair, eyes, and skin. The hair is often white or pale blond. However, it can be red, darker blond, light brown, or rarely, even dark brown. Vitiligo is a patchy loss of hair and skin color that may occur as the result of an
auto-immune disease An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part. At least 80 types of autoimmune diseases have been identified, with some evidence suggesting that there may be more than 100 types. Nearly a ...
. In a preliminary 2013 study, researchers treated the buildup of hydrogen peroxide which causes this with a light-activated pseudo-
catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...
. This produced significant media coverage that further investigation may someday lead to a general non-dye treatment for gray hair. Malnutrition 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 Werner syndrome (WS) or Werner's syndrome, also known as "adult progeria",James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. . is a rare, autosomal recessive disord ...
and pernicious anemia can also cause premature graying. A 2005 uncontrolled study demonstrated that people 50–70 years of age with dark eyebrows but gray hair are significantly more likely to have
type II diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urinatio ...
than those with both gray eyebrows and hair.


Artificial factors

A 1996
British Medical Journal ''The BMJ'' is a weekly peer-reviewed medical trade journal, published by the trade union the British Medical Association (BMA). ''The BMJ'' has editorial freedom from the BMA. It is one of the world's oldest general medical journals. Origina ...
study found that
tobacco smoking Tobacco smoking is the practice of burning tobacco and ingesting the resulting smoke. The smoke may be inhaled, as is done with cigarettes, or simply released from the mouth, as is generally done with pipes and cigars. The practice is believe ...
may cause premature graying. Smokers were found to be four times more likely to begin graying prematurely, compared to nonsmokers. Gray 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. There are no special diets, nutritional supplements, vitamins, or 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 patients with
imatinib Imatinib, sold under the brand names Gleevec and Glivec (both marketed worldwide by Novartis) among others, is an oral chemotherapy medication used to treat cancer. Imatinib is a small molecule inhibitor targeting multiple receptor tyrosine kin ...
, a new cancer drug, noted an unexpected side effect: some of the patients' hair color was restored to their pre-gray color.


Changes after death

The hair color of 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. The color of hair changes faster under extreme conditions. It changes more slowly under dry oxidizing conditions (such as in
burial Burial, also known as interment or inhumation, is a method of final disposition whereby a dead body is placed into the ground, sometimes with objects. This is usually accomplished by excavating a pit or trench, placing the deceased and objec ...
s in sand or in ice) than under wet reducing conditions (such as burials in wood or plaster coffins).


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. 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

*
Human skin color Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics (inherited from one's biological parents and or indiv ...


References


External links

{{Authority control Biological anthropology