![]() ![]() Much remains to be learned about the physiology of human graying. Gray hair may temporarily darken after inflammatory processes, after electron-beam-induced alopecia, and after some chemotherapy regimens. Smokers were found to be four times more likely to begin graying prematurely, compared to nonsmokers in the study. Mosley, MD found that tobacco smoking may cause premature graying. Artificial factors affecting hair colorĪ 1996 British Medical Journal study conducted by J.G. Werner syndrome and pernicious anemia can also cause premature graying.Ī 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 than those with both gray eyebrows and hair. The condition is reversible with proper nutrition. Dark hair may thus turn reddish or blondish due to the decreased production of melanin. Malnutrition is also known to cause hair to become lighter, thinner, and more brittle. Vitiligo is a patchy loss of hair and skin color that may occur as the result of an auto-immune disease. The skin is pale and the hair is white or pale blond. This results in gray, blue, or purple eyes. Other medical conditions affecting hair colorĪlbinism is a genetic abnormality in which little pigment is found in human hair, eyes or skin. The death of the melanocyte stem cells causes the onset of graying. The stem cells at the base of hair follicles are responsible for producing melanocytes, the cells that produce and store pigment in hair and skin. The change in hair color is caused when melanin ceases to be produced in the hair root and new hairs grow in without pigment. Two genes appear to be responsible for the process of graying, Bcl2 and Bcl-w. Sometimes people are born with gray hair because they inherit the trait genetically. The age at which graying begins seems to be almost entirely based on genetics. More than 40 percent of Americans have some gray hair by age 40, but white hairs can appear as early as childhood. Many blonde, strawberry blond, light brown, or red haired infants experience this.Ī change in hair color typically occurs naturally as people age, usually turning their hair to gray and then white. Hair color is genetically associated with certain skin tones and eye colors.Ĭhildren born with a certain color may find that it gradually darkens as they grow. Natural hair color is black, brown, blonde, or red, depending on a person's ethnic origins. A person's genotype for a multifactorial trait can interact with environment to produce varying phenotypes (see quantitative trait locus). ![]() Several gene pairs control the light versus dark hair color in a cumulative effect. The two-gene model does not account for all possible shades of brown, blonde, or red (for example, platinum blonde versus dark blonde/light brown), nor does it explain why hair color sometimes darkens as a person ages. Since the two gene pairs both govern hair color, 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 upon whether the first gene pair gives brown or blonde hair, respectively. The other gene pair is a not-red/red pair, where the not-red allele (which suppresses production of pheomelanin) is dominant and the allele for red hair is recessive. This also explains why two brown-haired parents can produce a blonde-haired child. A person with a brown allele will have brown hair a person with no brown alleles will be blonde. One gene, which is a brown/blonde pair, has a dominant brown allele and a recessive blonde allele. According to one theory, at least two gene pairs control human hair color. The genetics of hair colors are not yet firmly established. As the phaeomelanin continues to break down, the hair will gradually become orange, later yellow, and then white. This is the reason bleach will cause darker hair to turn reddish-brown during the artificial coloring process. Phaeomelanin is more chemically stable than black eumelanin, but less chemically stable than brown eumelanin, so it breaks down more slowly when oxidized. Although most noticeable in red-heads, all humans have varying concentrations of phaeomelanin in their hair. High amounts of black eumelanin results in black hair, while low concentrations of black eumelanin in the hair results in gray hair color. A low concentration of brown eumelanin in the hair results in blonde hair, whereas a higher concentration of brown eumelanin will color the hair brown. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color. There are two types of pigments that give hair its color: eumelanin and phaeomelanin. 3.3 Artificial factors affecting hair color.3.2 Other medical conditions affecting hair color.1 Genetics and biochemistry of hair color. ![]()
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