Premature greying of hair… also known as premature canities is increasingly common in general population since recent times. The cause could be multi-factorial and needs to be assessed. It could be genetic, environmental, stress-related, secondary to smoking, certain medications or some nutritional deficiencies. All these factors lead to underproduction of melanin that leads to grey or white hair. Practically, turning the grey here into black again is very difficult with medical treatment. However, with proper treatment you can avoid the progression of the problem and prevent further greying. Get an online consult privately with pictures or meet a dermatologist directly for a proper evaluation of the condition. Hope this was helpful.