Hair greying is a physiological process

Stress

1. release of numerous neurotransmitters in our fight or flight response
2. Cause DNA damage
3. promote aging and greying of hair.

Reason for hair greying

1. lntrinsic factors such as genetic defects, hormones, age etc or
2. extrinsic factors such as climate, pollutants, toxins, chemical exposure etc.

Premature hair greying

1. is basically hereditary and
2. inherited from parents or grandparents.

Hair follicle is

1. composed of specialized group of cells
2. melanocytes and keratinocytes
3. undergoes a cyclic process of degeneration and regeneration
4. Regulated by endocrine and paracrine mediators. 

Melanin pigments

1. produced by melanocytes
2. process called melanogenesis.
3. 2 types of melanin :

• eumelanin, dark brown or black,
• pheomelanin, reddish yellow. 
• Blend together - wide range of hair colours
• Pass the melanin to the keratin – producing cells called keratinocytes.

In younger people catalase breaks the hydrogen peroxide down into water and oxygen and removes it from the body.

With age melanocytes lose their ability to make pigment then the colour is absent from new hair.

Presence of superoxide dismutase ( SOD ) enzyme each of hair cells produce a tiny bit of hydrogen peroxide on their own.