Here are two causes of a fishy smelling vagina and one is an STI. An authoritative source
Bacterial vaginosis (BV): An infection that’s caused by an imbalance in your vagina’s flora. BV is responsible for the fishy smell most commonly associated with unpleasant vaginal odors. The fishy smell may be especially strong after sex. Another common symptom to look out for with BV is a gray or grayish-white discharge
Trichomoniasis: A sexually transmitted infection caused by a parasite. Trich doesn’t always cause symptoms. When it does, it can cause a fishy odor, similar to BV, or a musty smell. Another common symptom of Trich is a greenish-yellow discharge
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