Vagina itching before period goes away afterwards?

Possible infection. The bacterial balance in the vagina changes at different times of the menstrual cycle. This means that a vaginal infection from yeast or overgrowth of bacteria (bacterial vaginosis) can sometimes be more bothersome than other times during the menstrual cycle. I suspect you either have a yeast infection or bacterial vaginosis. The best way to determine this is to be seen by a health professional.