Premature greying is greying before the age of 30 yr. After that it is natural physiological process. There are various reasons involved in it. Genetic factor is the most important cause. Apart from that stress, nutritional deficiency. Thyroid problem increase it
it is very important to follow good nutritious diet. Hair require protein. Sprouts, beans, nuts are excellent source of protein. Green leafy vegetables give iron. Drink 3 lit of water/day. Melanin is the pigment which gives colour to hair. It is made up of protein.
Oiling is important as it conditions the scalp.
Consult trichologist for treatment.