Human hair color
Hair colors: black, brown, blonde, white, red.
Natural hair color can be black, brown, red, blond, or white.
Hair color is the pigmentation of hair follicles due to two types of melanin: eumelanin and pheomelanin.
If more melanin is present, the color of the hair is darker, and conversely, 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 vary over time causing a person’s hair color to change.
It is possible to have hair follicles of more than one color on the same person.
Hair colors are associated with some ethnic groups due to observed higher frequency of particular hair color within their geographical region: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, gray, white or silver hair is often associated with age and wisdom.
There are 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, synthesized by melanocytes.
reddish-brown/reddish-yellow pheomelanin, synthesized by melanocytes.
Eumelanin, has two subtypes of black or brown, which determine the darkness of the hair color; more black eumelanin leads to blacker hair, and more brown eumelanin to browner hair.
Pheomelanin colors hair orange and red.
Tyosine is converted into L-DOPA and then L-dopaquinone, which in turn is formed into pheomelanin or eumelanin inside the melanocytes.
Varied hair color phenotypes arise primarily as a result of differing ratios of these two pigments in the human population.
Europeans show the greatest range in pigmentation overall.
Other genetic and environmental factors can affect hair color in humans: 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 triggers increased synthesis pro-opiomelanocortin (POMC), α-MSH, and ACTH, the end result being increased eumelanin production.
Since UV radiation most commonly comes from the sun, populations from places closer to the equator tend to have darker hair.
Eumelanin is generally more photoprotective than pheomelanin.
All types of 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.
The Fischer–Saller scale, is used in physical anthropology and medicine to determine the shades of hair color.
Black hair
Natural black hair
Deepest brown hair
Dark brown hair
Medium brown hair
Natural brown hair
Light brown hair
Chestnut brown hair
Light chestnut brown hair
Auburn hair
Red hair
Orange red hair
Copper hair
Titian hair
Strawberry blond hair
Light blond hair
Golden blond hair
Medium blond hair
Gray hair
White hair
Brown-haired people have brown eumelanin, and also usually have medium-thick strands of hair.
Brown-haired girls or women are often known as brunettes.
Chestnut hair is common among the native peoples of Northern, Central, Western, and Eastern Europe.
Auburn hair are is associated with eumelanin (brown) and pheomelanin (red), with a higher proportion of red-causing pheomelanin than is found in average brown hair.
Auburn hair is most commonly found in individuals of Northern and Western European descent.
Auburn hair can also be the result of a mutation in the melanocortin 1 receptor gene.
Red hair ranges from light strawberry blond shades to titian, copper, and completely red.
Red hair has the highest amounts of pheomelanin, around 67%, and usually low levels of eumelanin.
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.
Scotland has the highest proportion of redheads; 13 percent of the population has red hair and
Approximately 40 percent of Scots carry the recessive redhead gene..
Blond 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.
Blond hair can have almost any
has only small amounts of both proportion of pheomelanin and eumelanin: 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 Western Europeans.
The naturally blond hair of Melanesians is caused by a recessive mutation in tyrosinase-related protein 1 (TYRP1).
White hair is commonly seen in elderly people, and is due to a lack of pigmentation and melanin: it is not caused by a true gray or white pigment.
The clear hairs appear as gray or white because the way light is reflected from the hairs.
Gray hair is a natural part of the aging process.
As we age, the pigment cells in our hair follicles gradually die, which leads to the hair losing its color and turning gray, white, or silver.
However, gray hair can also be caused by certain medical conditions, such as thyroid disorders or vitamin deficiencies.
Gray hair color typically occurs naturally as people age.
Gray hair may be caused by thyroid deficiencies, Waardenburg syndrome or a vitamin B12 deficiency.
At some point cells located in the base of the hair’s follicles slow, and eventually stop producing pigment, accounting for gray hair.
Piebaldism is a rare autosomal dominant disorder of melanocyte development, which may cause a congenital white forelock.
Europeans often begin to grow gray hairs in their mid-30s; Asians begin graying in their late 30s, but most Africans retain their original hair color until their mid-40s.
White hair starting in childhood can be genetically inherited, with no negative medical implications: 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.
Approximately 1 in 10 people have no gray hairs even after the age of 60.
Marie Antoinette syndrome refers to a proposed phenomenon in which sudden whitening is caused by stress: some hairs can become colored again when stress is reduced.
Children born with some hair colors may find it gradually darkens as they grow:
blond, light brown, or red haired infants may experience this.
This hair darkening is caused by genes being turned on and off during early childhood and puberty.
As people age turning the hair gray and then white 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.
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.
Skin pigment production is continuous.
Hair melanogenesis is closely associated with stages of the hair cycle: Hair is actively pigmented in the anagen phase turns off during the catagen phase, and absent during telogen.
Several genes are responsible for the process of graying.
Environmental factors control about 70% of cases of hair graying.
The stem cells at the base of hair follicles produce melanocytes, the cells that produce and store pigment in hair and skin.
The death of the melanocyte stem cells causes the onset of graying.
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 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 breaks down hydrogen peroxide and relieves oxidative stress in patients suffering from vitiligo.
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.
Imatinib has recently been shown to reverse the graying process.
The evidence for chronic stress causing premature achromotrichia,has not been established.
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
Albinism is a genetic abnormality in which little or no pigment is found in human hair.
The hair is often white or pale blond: it can be red, darker blond, light brown, or rarely, even dark brown.
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.
Improved nutrition may reverse this process.
Pernicious anemia can also cause premature graying.
Individuals 50-70 years of age with gray hair and dark eyebrows are significantly more likely to have type II diabetes than those with both gray eyebrows and hair.
Smokers are found to be four times more likely to begin graying prematurely, compared to nonsmokers.
Gray hair may temporarily darken after inflammatory processes, and after some chemotherapy regimens.
Imatinib side effect: some of the patients’ hair color was restored to their pre-gray color.
The hair color of buried bodies can change, as eumelanin is less chemically stable than pheomelanin and breaks down faster when oxidized.
Hair color can be changed by a chemical process: classed as permanent or semi-permanent.
Permanent hair: hair’s structure has been chemically altered until it is eventually cut away.
The natural color is removed, and synthetic color is put in its place.
All pigments subsequently wash out of the cuticle.
Natural color stays in much longer.
Permanent hair color gives can make hair lighter or darker as well as changing tone and color.
Monthly or six-weekly maintenance is essential to match new hair growing in to the rest of the hair, and to remedy fading.
Semi-permanent color washes out over a period of time—typically four to six weeks, so root regrowth is less noticeable.
With semi-permanent color the final color of each strand is affected by its original color and porosity, resulting in subtle variations in color across the head: more natural and less harsh than a permanent dye.
Gray and white hair will not dye to the same color as the rest of the head.
Some white hair will not absorb the color at all.
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.