You have developed premature greying(which you have figured already). This is a very common complaint these days. And what you need to know that the biggest factor is unhealthy lifestyle. Bad sleeping habits, eating habits and no exercise cause excessive oxidative stress on the body. And this causes premature aging (greying is a small part) . So modify your lifestyle... it will maybe help prevent future greying. It is difficult to turn your already white hair black. So I personally feel that focusing on improving your lifestyle works better. There are components like biotin and cal. Pantothenate that are 'assumed ' to work...but my experience says otherwise. Ideally, visit an allopathic dermatologist near you. Before you choose your dermatologist read the following 2 articles : http://www.skinmatra.com/single-post/2016/09/17/Listen-to-your-skin-talk-Here-is-how  And this one : http://www.skinmatra.com/single-post/2016/07/03/Skin-Troubles-Here-is-WHAT-NOT-TO-DO