Human hair color

Its tone depends on the ratio of black or brown eumelanin to yellow or red pheomelanin.

[citation needed] The full genetic basis of hair color is complex and not fully understood.

[3] Two types of pigment give hair its color, black-brown eumelanin and reddish-brown/reddish-yellow[4] pheomelanin, synthesized by melanocytes.

[5] Inside the melanocytes, tyrosine is converted into L-DOPA and then L-dopaquinone, which in turn is formed into pheomelanin or eumelanin.

[6] UV radiation most commonly comes from the sun, and thus populations from places closer to the equator tend to have darker hair,[6] because eumelanin is generally more photoprotective than pheomelanin.

[9] Pheomelanin is generally found in elevated concentrations in blond and red hair,[4] representing about one-third of total melanin content.

[10] The Fischer–Saller scale, named after Eugen Fischer and Karl Saller is used in physical anthropology and medicine to determine the shades of hair color.

It has large amounts of eumelanin and is denser than other hair colors 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.

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.

Brown-haired girls or women of European, West Asian or North African descent are often known as brunettes.

It is most commonly found in individuals of Northern and Western European descent, but is extant in West and Central Asia and North Africa also.

[citation needed] Blond hair can have almost any proportion of pheomelanin and eumelanin, but has only small amounts of both.

Studies in 2012 showed that naturally blond hair of Melanesians is caused by a recessive mutation in tyrosinase-related protein 1 (TYRP1).

Marie Antoinette syndrome is a proposed phenomenon in which sudden whitening is caused by stress.

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.

Sometimes a mixture of dyes is used while hair is greying: semi-permanent as a base color, with permanent highlights.