Odor can also come from the bacteria that naturally accumulates during your period. "When you’re bleeding, you retain moisture in the vagina ," Dr. Shirazian says, which can lead to "secondary vaginal infections like bacterial vaginosis, which has a strong, fishy odor." The thing to remember about bacterial vaginosis (sometimes shortened to BV) is that it occurs when the bacteria that's normally found in your vagina is out of balance, and can either go away on its own or be treated with antibiotics. While BV itself isn't an STI , it is known to increase your risk for catching an STI, so if you are experiencing odor, itching, or painful urination, you should definitely see your doctor for treatment. And, if you notice an out-of-the-ordinary odor when you aren't menstruating, you might want to talk to your doctor. You may have BV, vaginitis , or some other kind of infection that requires treatment.