Why does my vagina have an extremely foul odor?

Reviewed by Yoshinori Abe, MD

Internal Medicine

A very strong or foul vaginal odor often signals a disruption in the vagina's natural bacterial balance. The most common cause is bacterial vaginosis (BV), an infection that typically produces a distinct "fishy" smell, especially after intercourse. Other possible causes include trichomoniasis, a retained tampon, poor hygiene, or, in rare cases, trimethylaminuria (also known as fish odor syndrome), a metabolic disorder.

Because vaginal odor can point to several different conditions—each requiring different treatment—it's important not to guess. A free, instant, online symptom check can help you quickly narrow down possible causes based on your specific symptoms and guide you on the right next steps, whether that means seeing a doctor, adjusting a habit, or seeking urgent care. Understanding what's going on is the first step toward feeling like yourself again.

Reviewed for medical accuracy: 07/15/2026

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Explanation

Your vagina normally has a mix of good bacteria that keep it clean and maintain a gentle natural smell. When this balance is upset, it can lead to the release of chemicals such as trimethylamine.

In bacterial vaginosis, for example, the healthy bacteria called lactobacilli decrease while other bacteria proliferate, producing trimethylamine that gives off a strong, foul, fishy odor. In some rare cases, a condition known as fish odor syndrome (trimethylaminuria) may cause a very strong foul odor because the body cannot break down trimethylamine properly.

Research shows that even factors like changes in the vaginal lining or infections, including HPV, might alter the natural defenses in the vagina and contribute to odor. If you experience an extremely foul odor that is unusual for your body, you can start by using a free symptom checker to better understand your symptoms before talking to a healthcare provider. They can do tests, check for infections, and determine if any treatment is needed to restore a healthy balance and help you feel comfortable.

(References)

Wolrath H, Borén H, Hallén A, Forsum U. Trimethylamine content in vaginal secretion and its relation to bacterial vaginosis. APMIS. 2002 Nov;110(11):819-24. doi: 10.1034/j.1600-0463.2002.1101108.x. PMID: 12588422.
Li M, Al-Sarraf A, Sinclair G, Frohlich J. Fish odour syndrome. CMAJ. 2011 May 17;183(8):929-31. doi: 10.1503/cmaj.100642. Epub 2011 Mar 21. PMID: 21422137; PMCID: PMC3091902.
Lebeau A, Bruyere D, Roncarati P, Peixoto P, Hervouet E, Cobraiville G, Taminiau B, Masson M, Gallego C, Mazzucchelli G, Smargiasso N, Fleron M, Baiwir D, Hendrick E, Pilard C, Lerho T, Reynders C, Ancion M, Greimers R, Twizere JC, Daube G, Schlecht-Louf G, Bachelerie F, Combes JD, Melin P, Fillet M, Delvenne P, Hubert P, Herfs M. HPV infection alters vaginal microbiome through down-regulating host mucosal innate peptides used by Lactobacilli as amino acid sources. Nat Commun. 2022 Feb 28;13(1):1076. doi: 10.1038/s41467-022-28724-8. PMID: 35228537; PMCID: PMC8885657.

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