A fishy vaginal odor is almost always caused by bacterial vaginosis (BV), a condition where the balance of bacteria in the vagina shifts away from the protective species that keep things in check. About 30% of women of reproductive age have BV at any given time, and while it sometimes resolves on its own, most cases need treatment to fully clear the smell. Here’s what causes it and how to get rid of it.
Why It Smells Fishy
A healthy vagina is dominated by Lactobacillus bacteria, which produce lactic acid and keep the environment slightly acidic (a pH below 4.5). When those bacteria lose their foothold, other organisms move in and produce compounds called amines as they grow. Those amines are what create the fishy smell, and it often gets stronger after sex or during your period because semen and menstrual blood are both alkaline, which releases more of the odor.
BV is by far the most common cause, but trichomoniasis, a sexually transmitted infection, can also produce a fishy smell. The two look slightly different: BV typically causes a thin, white or gray discharge, while trichomoniasis is more likely to cause itching, redness, soreness, and sometimes a frothy or greenish discharge. Both can burn during urination. If you’re not sure which you’re dealing with, a healthcare provider can tell them apart quickly with a simple exam.
Getting Treated for BV
Prescription antibiotics are the most reliable way to eliminate BV and the smell that comes with it. The two main options are an oral antibiotic taken once daily for seven days, or an antibiotic vaginal cream applied at bedtime for three to seven days. Both are highly effective. Your provider will choose based on your preferences, whether you’re pregnant, and whether you’ve had BV before.
Most people notice the smell fading within a couple of days of starting treatment, though you should finish the full course even after symptoms improve. Stopping early increases the chance of the infection coming back.
Why BV Keeps Coming Back
Recurrence is the most frustrating part of BV. More than half of women who are treated will have another episode within 12 months. The bacteria that cause BV can form a protective layer on the vaginal walls that antibiotics don’t always fully penetrate, which is why the infection returns.
For people dealing with repeated episodes, providers sometimes recommend a longer course of treatment or a maintenance regimen where you use a vaginal gel periodically after the initial infection clears. Boric acid vaginal suppositories are another option sometimes used alongside or after antibiotics. Boric acid helps restore vaginal acidity and can relieve itching, burning, and odor. It’s important to know that boric acid is only for vaginal use and is toxic if swallowed. You should also avoid using it if you’re pregnant or trying to become pregnant, and skip sex or tampon use during treatment since it can interfere with condoms, diaphragms, and spermicides.
Habits That Protect Your Vaginal Balance
The vagina is self-cleaning, and many of the things marketed to “freshen” it actually make the problem worse. Douching is one of the strongest risk factors for developing BV. It strips away the protective Lactobacillus bacteria and raises vaginal pH, creating the exact conditions that allow odor-causing bacteria to thrive. The World Health Organization lists douching and inserting herbs or other products into the vagina as direct risk factors for BV.
Scented soaps, body washes, sprays, and wipes applied to the vulva or inside the vagina can do the same thing. Clean the external area with warm water alone, or with a mild, fragrance-free soap on the outer skin only. Nothing needs to go inside.
Other practical steps that help maintain a healthy bacterial balance:
- Wear breathable underwear. Cotton or moisture-wicking fabrics keep the area dry and discourage bacterial overgrowth.
- Change out of wet clothing quickly. Sitting in a damp swimsuit or sweaty workout clothes creates a warm, moist environment that shifts bacterial balance.
- Use condoms with new partners. Unprotected sex with a new or multiple partners is a well-established risk factor for BV. Semen temporarily raises vaginal pH, and exposure to a new partner’s bacteria can disrupt your existing flora.
- Wipe front to back. This prevents introducing bacteria from the rectum into the vaginal area.
Diet and Vaginal Health
What you eat may play a bigger role than most people realize. Research published in Frontiers in Cellular and Infection Microbiology found that diets high in simple sugars like glucose and fructose were linked to lower levels of protective Lactobacillus crispatus bacteria in the vagina. When Lactobacillus levels drop, glucose concentrations in vaginal fluid rise, and that extra glucose feeds the very bacteria associated with BV and fishy odor.
Higher dietary fat intake and higher glycemic load have also been associated with increased BV risk. On the other hand, some research in pregnant women found that higher total carbohydrate intake from varied sources (not just refined sugar) was actually protective, suggesting the issue is specifically with high-sugar, high-fat diets rather than carbohydrates in general. A diet rich in whole foods, vegetables, and fiber supports the kind of bacterial environment that keeps odor in check.
Probiotics for Vaginal Flora
Probiotic supplements aimed at vaginal health have become popular, and there is some science behind them. The strains with the most research support include Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14, which have been studied specifically for restoring vaginal bacterial balance. Lactobacillus crispatus and Lactobacillus acidophilus also show up frequently in clinical research on BV prevention.
Probiotics are available as oral capsules or vaginal suppositories. They’re generally used as a complement to antibiotic treatment rather than a replacement, especially for recurrent BV. There’s no universally agreed-upon dose, but most studied formulations contain billions of colony-forming units per dose. Probiotics alone are unlikely to clear an active infection with strong odor, but they may help prevent the next one.
When the Smell Isn’t BV
If you’ve been treated for BV and the smell persists, or if the odor is accompanied by unusual symptoms, other causes are worth considering. Trichomoniasis requires a different antibiotic than BV and won’t respond to standard BV treatment. A forgotten tampon (more common than you’d think) can produce an intense fishy or rotten smell and needs to be removed by a provider if you can’t reach it yourself. Rarely, cervical or vaginal infections unrelated to BV can cause persistent odor.
A mild, musky vaginal scent is completely normal and varies throughout your menstrual cycle. The smell you’re trying to get rid of is specifically the strong, fishy one, and in most cases, a short course of treatment combined with the hygiene adjustments above will resolve it.