Thanks for consulting. I have carefully worked through your case, and I can realize your health worries. Being your physician, I assure you not to worry as I will take care all of your medical concerns. premature graying usually happens atlest by teen age but at this age it is pretty much so early. it must be due to genetic or inherited cause. consult a dermatologist as the cause has to be ruled out. vitamin tablets like biotin can help delay it. Hope it helps. If you need further, detailed and quick assistance related to any health issues in future, feel free to ask me a question directly from my profile. Have a wonderful time ahead. Best Regards! Dr. Arunmozhi varman