What does BV smell like? Fishy. Bacterial vaginosis has a distinct fishy, slightly ammonia-like smell that is usually strongest right after sex and during or after your period, often with thin grey-white discharge. A healthy vagina has a smell too: mildly sour or tangy. That normal smell is the one most often mistaken for a problem, and the fishy one is the one most often covered up instead of tested.
Below: why BV smells the way it does, how to tell fishy from sour, metallic and yeasty, why BV gets louder after sex, why most BV doesn't smell at all, and what helps.
What does bacterial vaginosis smell like, and why fishy?
BV isn't one germ. It's a community shift: the Lactobacillus that normally dominate and keep vaginal pH around 3.8–4.5 lose ground to a mix of anaerobic bacteria such as Gardnerella, Prevotella and others. Those bacteria produce biogenic amines, mainly trimethylamine (the compound behind the smell of fish), putrescine and cadaverine. Women with BV-type communities have more of them (Nelson 2015).
pH decides how much of that you smell. In an acidic vagina, amines stay dissolved as non-volatile salts. When pH rises, they're released as gas. That's the whole basis of the clinician's "whiff test": add an alkaline solution (10% KOH) to a sample of discharge and see if a fishy odor appears.
The whiff test is one of the four Amsel criteria clinicians use. BV is diagnosed when at least three are present (CDC):
- Thin, milky, uniform discharge that coats the vaginal walls
- Clue cells (vaginal cells studded with bacteria) under the microscope
- Vaginal pH above 4.5
- A fishy odor before or after the whiff test
So the smell is a real signal, but on its own it isn't a diagnosis.
Fishy vs sour vs metallic: what each vaginal smell means
Sour or tangy
A sour vaginal smell is usually the healthy one. Lactobacillus make lactic acid; that is what keeps your pH low and what you're smelling. It can be stronger after a workout, in tight or synthetic underwear, or at the end of the day. Sour smell plus thick white discharge and itching points more toward yeast than BV.
Fishy
The classic BV smell. The other common cause is trichomoniasis, a sexually transmitted infection: the CDC lists a clear, white, yellowish or greenish discharge "with a fishy smell", often with itching, soreness or discomfort when peeing, and notes that about 70% of people with trich have no symptoms at all. A faint fishy note that appears briefly after sex or during your period and then fades can be the same amine chemistry without BV (more below).
Metallic or coppery
Blood. Your period, spotting, brown discharge at the end of a period, or tiny friction tears after sex. Normal unless bleeding is unexpected.
Bready or yeasty
Yeast infections usually have little or no odor. The CDC's list of typical yeast symptoms is itching, soreness, pain with sex, burning on the skin when you pee and abnormal discharge; odor isn't on it, and yeast infections sit at a normal pH (below 4.5).
Rotten or truly foul
A smell that is foul and doesn't wash off can mean a forgotten tampon or other retained object. That needs to come out the same day; fever, rash, vomiting or dizziness with it means urgent care.
Sweaty or musky
Often not vaginal at all. The groin and vulva have apocrine sweat glands, and sweat and sebum broken down by skin bacteria smell musky or oniony. See odor below the belt and why sebum smells.
My discharge smells bad but not fishy
Work out where the smell actually comes from before deciding what it is:
- Fresh vs old. Discharge on a liner or underwear at the end of the day has been sitting warm and oxidizing. Fresh discharge on clean fingers is the fair test.
- Vagina vs skin. Musky or sweaty usually means skin folds and sweat, not discharge.
- Urine. Concentrated urine smells of ammonia and is easy to confuse with discharge.
- Sour is fine. Sour or tangy discharge without itching or burning is usually normal flora.
- Foul or rotten needs a check, as above.
Any new discharge that is grey, green, yellow, frothy or comes with itching, burning or pain is worth testing regardless of smell.
BV after sex: why the smell gets worse
Semen is alkaline. After sex without a condom, it pushes vaginal pH up for hours, and that releases amines exactly the way the whiff test does. That's why BV that is quiet the rest of the time often shows up first as a fishy smell after sex, and why many women first notice it with a new partner.
Why do I get BV after sex? Sex doesn't just make BV easier to smell; it's linked to getting it. A meta-analysis of sexual risk factors found BV associated with new and multiple male partners and with female partners, and condom use associated with lower risk (Fethers 2008). The CDC lists the same associations. BV isn't classed as an STI, and the CDC doesn't recommend routine treatment of male partners, but sex clearly moves the vaginal microbiome.
Things that add to the load around sex:
- Semen (alkaline) and saliva
- Lubes that are hyperosmolar or contain glycerin and harsh preservatives, which irritate tissue and stress Lactobacillus (details in can lube cause a yeast infection or BV?)
- Douching or scented washes "to clean up" afterward
If the lube is part of your routine, use one that works with your pH rather than against it. Juicy Balance is glycerin-free, propylene-glycol-free and fragrance-free, buffered to pH 4.5–4.9 with gluconolactone, and osmolality-tested at about 296 mOsm/kg, close to your body's own. It also contains lactoferrin and xylitol, with carrageenan for glide. In our 5-day tester round, 4 of 5 testers had a higher share of Lactobacillus afterward (see the results). Individual results from a small, uncontrolled sample; not intended to diagnose, treat, cure, or prevent any disease.
A fishy smell after sex that fades within a day and never comes with new discharge isn't necessarily BV. That case has its own post: vaginal odor after sex without infection.
Does BV always smell?
No. In a nationally representative US survey (NHANES 2001–2004), 29.2% of women aged 14–49 had BV, and 84% of them reported no symptoms (Koumans 2007). The CDC summarizes it the same way: most women with BV are asymptomatic.
So "BV with no smell" is common, and so is BV that smells only some of the time: after sex, during your period (blood is alkaline too), or after a scented product. Absence of smell doesn't rule BV out. It's worth testing even without odor if you're pregnant, have a procedure coming up, or have recurring discharge.
Smell isn't a diagnosis: how to check
- Home pH strip. A reading above 4.5 fits BV or trich; yeast usually reads normal. Test away from sex, your period and lube, which all push the number up.
- Clinic. Amsel criteria or a Gram stain for BV; a lab test for trich, since its symptoms overlap with BV.
- Microbiome sequencing. Shows which bacteria dominate. Useful if BV keeps coming back, not a substitute for a diagnosis.
What helps with BV smell
Diagnosed BV is treated with prescription antibiotics (usually metronidazole or clindamycin), and recurrence is common, so the CDC advises coming back if symptoms return. Around that, a few things make a difference:
Stop covering it up
Douching, scented washes, sprays and home remedies inside the vagina (vinegar, garlic, tea tree) mask the smell briefly and disturb the flora further. The CDC notes douching might increase the risk of relapse and that no data support it for symptom relief.
Wash the outside only
Water or a fragrance-free cleanser on the vulva, nothing inside. Our WASH is fragrance-free and prebiotic, made to clean without stripping the skin's own bacteria.
Cut the alkaline load around sex
Condoms during treatment and the weeks after keep semen out while your pH recovers. Skip high-osmolality, glycerin-based lubes.
Support Lactobacillus after treatment
Antibiotics clear the BV bacteria; your Lactobacillus still have to take the space back. Our Suppository combines vagina-friendly probiotic strains with lactoferrin and hyaluronic acid in a cocoa butter base, one at bedtime for 5 nights. One tester's before-and-after is in Five days to reset. Individual results from a small, uncontrolled sample; not intended to diagnose, treat, cure, or prevent any disease. It's microbiome support, not a treatment for BV: get diagnosed first. Why lactoferrin matters here: lactoferrin and the vaginal microbiome.
When to see a clinician
- A fishy smell that lasts more than a couple of days, or keeps coming back after sex or every period
- Thin grey-white, green, yellow or frothy discharge
- Itching, burning, soreness or pain when you pee alongside the smell
- A foul smell you can't wash off, or a tampon you can't find
- Pelvic pain or fever
- You're pregnant
- A new partner and any new symptom (test for trich and other STIs, not just BV)
If sex is when the smell shows up, look at what goes in along with it. Try Juicy Balance: pH 4.5–4.9, glycerin-free, close to body osmolality, rinses off with water.
FAQ
Is a sour vaginal smell normal?
Yes, in most cases. A mildly sour or tangy smell is lactic acid from Lactobacillus, the bacteria that keep your vagina acidic. It becomes a question only if it changes noticeably or comes with itching, burning or new discharge.
Does a yeast infection smell fishy?
Usually not. Yeast infections tend to have little odor and a normal pH. Itching plus a fishy smell can mean BV and yeast at the same time, or trichomoniasis, so get tested rather than reaching for an antifungal.
Why does BV smell come back after sex or my period?
Semen and menstrual blood are both alkaline. They raise vaginal pH, which releases the amines BV bacteria produce. If the smell keeps returning on that schedule, BV may not have fully cleared or may be recurring; ask for testing while you have symptoms.
Related reading
- Why does my vagina smell?
- Vaginal odor after sex, without infection
- Can lube cause a yeast infection or BV? Or is it irritation?
- pH-balancing products: what they do
Sources
- Nelson TM, et al. Vaginal biogenic amines: biomarkers of bacterial vaginosis or precursors to vaginal dysbiosis? Front Physiol. 2015;6:253. doi:10.3389/fphys.2015.00253
- Koumans EH, et al. The prevalence of bacterial vaginosis in the United States, 2001–2004; associations with symptoms, sexual behaviors, and reproductive health. Sex Transm Dis. 2007;34(11):864-869. doi:10.1097/OLQ.0b013e318074e565
- Fethers KA, et al. Sexual risk factors and bacterial vaginosis: a systematic review and meta-analysis. Clin Infect Dis. 2008;47(11):1426-1435. doi:10.1086/592974
- CDC. Bacterial vaginosis, STI Treatment Guidelines 2021. cdc.gov
- CDC. Vulvovaginal candidiasis, STI Treatment Guidelines 2021. cdc.gov
- CDC. About trichomoniasis. cdc.gov