Published on: 3/17/2025
A common cause of white vaginal discharge that smells is bacterial vaginosis, where an imbalance in the natural bacteria causes the discharge to develop a fishy smell from a chemical called trimethylamine. Other types of infections can sometimes also cause unusual odors.
When the normal balance of good bacteria in the vagina changes, a condition called bacterial vaginosis can develop. In this condition, the numbers of bacteria that help protect the vagina drop, and other bacteria that produce a strong chemical called trimethylamine can grow. This chemical often causes a fishy smell in the discharge. Sometimes, other infections like trichomoniasis might also cause an odor and other symptoms like itching or irritation. Yeast infections mostly lead to thick, white, cottage cheese–like discharge and typically do not have a strong smell. However, if you notice a new or unusual smell along with white vaginal discharge, it might be because the balance of bacteria in the vagina is off, leading to the production of the odor-causing chemical. It is important to talk with a health care provider if you have any concerns about changes in vaginal discharge or smell.
(References)
Brand JM, Galask RP. Trimethylamine: the substance mainly responsible for the fishy odor often associated with bacterial vaginosis. Obstet Gynecol. 1986 Nov;68(5):682-5. PMID: 3763085.
Bishop GB. Vaginal Discharge. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 172. Available from: https://www.ncbi.nlm.nih.gov/books/NBK281/
Ries AJ. Treatment of vaginal infections: candidiasis, bacterial vaginosis, and trichomoniasis. J Am Pharm Assoc (Wash). 1997 Sep-Oct;NS37(5):563-9. doi: 10.1016/s1086-5802(16)30241-8. PMID: 9479409.
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