Jun 10, - If that scent becomes unpleasant, though, it could indicate a problem. Here are the five most common causes of unpleasant vaginal odor, and. Bacterial vaginosis — an overgrowth of normally occurring vaginal bacteria — is the most common vaginal infection that causes a vaginal odor. Trichomoniasis — a sexually transmitted infection — also can lead to vaginal odor. Chlamydia and gonorrhea infections usually don't cause vaginal odors.