I was told by someone to use Niacin as a blood circulating supplement. I tried it today and WOW that stuff really works!! I must admit that I was scared upon the first reaction. My scalp started tingling and my whole body felt really hot. I know it sounds scary but it lasted for about 5 mins. Niacin is used in a lot of hair growth vitamins, I bought the GNC 500 mg. Has this happened to anyone?