Grey hair is simply the loss of pigment (melanin) that gives hair its colour — it is the absence of colour. Melanin is the same thing that gives skin its colour, while increased melanin production is what creates a tan. When and why hair turns grey is a little more complex.

Causes of Greying

Aging is the main cause of greying hair, but health and heredity can be factors as well. With age, the body produces a reduced amount of melanin. Hair grows out of hair follicles, which contains cells filled with melanin (called melanocytes). Over time, as hair follicles produce less melanin, the new hair grows out more grey.

Genetics plays a role—if your parents went grey early, you have a higher chance too. Your health is also a determining factor, so grey hair can signal an underlying medical condition associated with decreased melanin production. For example, vitiligo is marked by the loss of skin pigmentation (through the death of melanocytes), and it can also cause hair to lose its pigment in some cases.

Anything that contributes to hair loss can help reveal grey hair that was previously hidden from view, since dark hair tends to fall out more readily than grey hair. Some medications, such as lithium and methotrexate, can also cause hair loss.

Greying Hair Facts
  • Men go grey earlier, about age 30, and women at around 35.
  • Grey hairs first show up around temples and top of head.
  • Each hair grows for 2 to 4 years, and then falls out shortly thereafter.
  • People typically lose 50 to 100 hair strands each day.
  • Smoking tends to make hair go grey sooner.