welcome to hcm,
as per the details u have been given, u are having PREMATURE GRAYING OF HAIR.
there are lot of reasons for causing premature graying of hair like Nutritional problems, familial, zinc and B-vitamin deficiency
, pollution, excessive stress
. but there is no specific reason that a person would get gray hair.
and more imporatantly THERE IS NO SPECIFIC TREATMENT FOR GRAY HAIR,...OK ..dont believe that some body coming up with some pills or oral powders that they will treat ur gray hair.
one interesting thing is u can reduce the graying by avoiding stress, taking good nutritive food , taking fruits...
i think this will help u a lot.