Why does hair turn gray?

It is well known that gray hair results from a reduction of pigment, while white hair has no pigment, but why this happens remains somewhat of a mystery.

Parents often cite having teenagers as the cause of gray hair. This is a good theory, but scientists continue to investigate why hair turns gray. In time, everyone’s hair turns gray. Your chance of going gray increases 10-20% every decade after 30 years.

Initially, hair is white. It gets its natural color from a type of pigment called melanin. The formation of melanin begins before birth. The natural color of our 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:

• Anagen: This is the active growth stage of the hair fiber and can last from 2- 7 years. At any given moment 80-85% of our hair is in the anagen phase.
  
  
• Catagen: 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.
  
  
• Telogen: This occurs when hair growth is completely at rest and the hair fiber 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 anagen phase.

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 a colorful hue.

With age comes a reduction of melanin. The hair turns gray and eventually white.