I think if you dont have a yeast problem, b vitamins shouldn't be an issue but if you do they can cause an outbreak to get worse. My topical yeast ALWAYS got worse when I took lots of b vitamins and C. I mean think about it yeast flakes are known for their great vitamin b content because the yeast consume it for food. the reason why I wanted to post this on the site is because I've seen many people who seem to megadose with these vitamins and I think if you have candida its doing much more harm then good.