Why does hair go grey?

Grey hair is caused by a reduction of pigmentation, whereas white hair has no pigment all. Why this happens at all remains somewhat of a mystery.

In time, everyone’s hair turns grey eventually and your chances of going grey increases by 10-20% every decade after 30 years.

Fundamentally, hair is white. It then gets its natural color from a pigment called melanin. The formation of melanin begins before birth and is also responsible for your skin color and tanning in the sun. The natural color of your hair depends upon the distribution, type and amount of melanin in the middle layer of the hair shaft or cortex.

Hair has only two types of pigments: dark (eumelanin) and light (phaeomelanin). They blend together to make up the wide range of hair colors.

Melanin is made up of specialized pigment cells called melanocytes. They position themselves at the openings on the skin’s surface through which hair grows (follicles). Each hair grows from a single follicle.

The process of hair growth has three phases:

* Anagenic phase: This is the active growth stage of the hair fibre and can last from 2- 7 years. At any given moment 80-85% of our hair is in the anagen phase.

* Catagenic phase: Sometimes referred to as the transitional phase, which is when hair growth begins to “shut down” and stop activity. It generally lasts 10- 20 days.

* Telogenic phase: This occurs when hair growth is completely at rest and the hair falls out. At any given time, 10-15 % of our hair is in the telogen phase, which generally lasts 100 days for scalp hair. After the telogen phase, the hair growth process starts over again to the anagenic phase. The extension of the telogenic phase has also been quoted as a cause of hair loss,

As the hair is being formed, melanocytes inject pigment (melanin) into cells containing keratin. (Keratin is the protein that makes up our hair, skin, and nails). Throughout the years, melanocyctes continue to inject pigment into the hair’s keratin, giving it color.

With age comes a reduction of melanin. There is less melanin so the hair turns grey and eventually white.

So why does hair turn grey or white?

Dr. Desmond Tobin, professor of cell biology from the University of Bradford(UK), suggests that the hair follicle has a “melanogentic clock” which slows down or stops melanocyte activity, thus decreasing the pigment our hair receives. This also occurs just before the hair is preparing to fall out or shed, so the roots always look pale.

Unsurprisingly, Dr. Tobin suggests that hair turns grey because of age and genetics, and genes regulate the exhaustion of the pigmenting potential of each individual hair follicle. This occurs at different rates in different hair follicles. For some people it occurs rapidly, while in others it occurs slowly over several decades.

Harvard scientists proposed that a failure of melanocyte stem cells to maintain the production of melanocytes could cause the greying of hair. This failure of melanocyte stem cell maintenance may result in the breakdown of signals that produce hair color.

In 2009, European scientists described how hair follicles produce small amounts of hydrogen peroxide. This bleaching chemical builds on the hair shafts, which can lead to a gradual loss of hair color.

In summary therefore it appears that hair goes grey via two mechanisms both related to age, the first being a reduction in the pigment (melanin) which gives the hair its color and also an increase in hydrogen peroxide which actually has a bleaching effect upon the hair follicle.

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