Bacterial vaginosis (BV) shows up as a thin white or gray discharge, a strong fish-like odor that gets worse after sex, and sometimes itching, burning, or a sting when you pee. Many people have no symptoms at all. BV happens when normal vaginal bacteria are crowded out by other bacteria. It's common and treatable.
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Thin white or gray discharge
most recognizable sign
-
Strong fishy odor
especially noticeable after sex (amines meet semen pH)
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Itching or burning around the vagina
external, not deep
-
Burning when urinating
less common; overlaps with UTI symptoms
-
No symptoms
~50% of cases — found only when tested for another reason
| Item | Value |
|---|---|
| Thin white or gray discharge | — most recognizable sign |
| Strong fishy odor | — especially noticeable after sex (amines meet semen pH) |
| Itching or burning around the vagina | — external, not deep |
| Burning when urinating | — less common; overlaps with UTI symptoms |
| No symptoms | — ~50% of cases — found only when tested for another reason |
What BV actually is — the imbalance behind the symptoms
A healthy vagina is dominated by Lactobacillus bacteria, which make lactic acid and keep the environment acidic. That acidity is protective. In BV, those lactobacilli get replaced by a mix of anaerobic bacteria, and the vaginal pH climbs out of its normal acidic range CDC, About BV. Almost every classic BV symptom traces back to that single shift: fewer acid-makers, more odor-makers, a less acidic environment.
BV is the most common vaginal condition in women ages 15 to 44. It isn't classified as a traditional sexually transmitted infection, but it's tightly linked to sexual activity. New or multiple partners can disrupt the bacterial balance, and women who've never been sexually active rarely get it.
What the symptoms are — and what each one means
Thin white or gray discharge
BV discharge is usually thin and runny rather than thick, and it ranges from off-white to gray. It often coats the vaginal walls evenly, so you may notice more on underwear or after a shower. This differs from the thick, clumpy discharge of a yeast infection. If you're trying to tell them apart, see our breakdown of yeast vs bv discharge.
A strong fishy odor, especially after sex
The fish-like smell is the most recognizable BV sign, and it's pure chemistry. The anaerobic bacteria release compounds called amines. When those amines hit something alkaline like semen during sex or menstrual blood, they volatilize and the odor spikes. That's why so many people first notice BV right after intercourse or around their period.
Itching, burning, or irritation
Some people feel external itching or a burning sensation around the vaginal opening. It tends to be milder than the intense itch of yeast, and the irritation comes from the disrupted, less acidic environment.
Burning when you urinate
A sting or burn during urination can happen as urine passes over irritated tissue. Because this overlaps with a urinary tract infection, it's easy to misread, so test rather than guess.
No symptoms at all
Many people with BV have no symptoms whatsoever. Symptom-free BV still raises certain health risks, so it sometimes gets picked up during a routine exam or another test.
Where symptoms show up — and the less obvious signs
BV symptoms center on the vagina and vulva: the discharge, the odor, and external itch or burning. The odor is often the first thing people notice, sometimes before any discharge change, because ordinary events like sex or menstruation trigger it. Less obvious clues include a smell that comes and goes with your cycle, or irritation you blame on a new soap, laundry detergent, or underwear. BV doesn't cause pelvic pain, fever, or sores; if you have those, something else is going on and you should be evaluated.
How soon symptoms appear
BV isn't caught from a single exposure the way a classic infection is, so there's no fixed incubation window. It develops when the bacterial balance tips, which can follow a new partner, a change in partners, douching, or sometimes no clear trigger at all. Symptoms can surface within days of that shift or build gradually. If you're tracking symptoms against a specific encounter, our guide on when to test after exposure explains how timing works for infections that do have set windows.
What people mistake BV for
BV is the condition most often confused with a yeast infection, and treating the wrong one is a classic mistake, because an over-the-counter antifungal does nothing for BV. The two feel different once you know the cues.
| Feature | Bacterial vaginosis | Yeast infection |
|---|---|---|
| Discharge | Thin, white or gray, coats the walls | Thick, white, clumpy (cottage-cheese-like) |
| Odor | Strong, fishy — worse after sex | Little or no odor |
| Itch | Mild, if any | Intense itching common |
| Burning when peeing | Sometimes | Sometimes |
| Treated with | Antibiotics | Antifungals |
People also mistake BV for a urinary tract infection because of the burning, for a sexually transmitted infection like trichomoniasis that can also cause odor and discharge, or for normal cyclical changes. A quick test settles it. Guessing wastes time and can make recurrence worse.
Complications if BV goes untreated
BV is more than a nuisance. Losing protective lactobacilli changes the vaginal environment in ways that matter for your wider health:
- BV raises the risk of acquiring or transmitting HIV and other STIs. A meta-analysis of more than 30,000 women found BV increased the risk of acquiring HIV by about 60% Atashili et al., AIDS.
- In pregnancy, BV is linked to a higher risk of preterm delivery and low birth weight, so pregnant people with symptoms should be evaluated.
- BV can increase the risk of infection after gynecologic procedures.
Recurrence is the other problem. Standard antibiotics cure most acute episodes, but BV comes back in a large share of women within a year CDC STI Tx Guidelines, 2021. Recurrent BV, defined as three or more episodes a year, often needs a months-long maintenance regimen rather than another single course SASGOG. If you keep cycling through episodes, that's worth discussing; see your options for bv treatment.
Who should get checked
There's no universal screening program for BV in people without symptoms, but get evaluated if you have the symptoms above, if a previous episode keeps returning, or if you're pregnant and notice discharge or odor changes. Because symptom-free BV still carries the HIV and pregnancy risks, mention any abnormal smell or discharge during routine visits, and a clinician can check even when you're unsure.
How BV is tested
Diagnosis is quick. A clinician examines a sample of discharge, checks vaginal pH, and looks for clue cells under a microscope, or runs a lab test, with results usually back within a few days. For the full walkthrough of methods and what to expect, see our page on bv testing.
When to see a clinician
Get checked if you have a new or strong fishy odor, an unusual discharge, itching or burning that isn't going away, symptoms after a new partner, or anything that returns after treatment. Don't self-treat with an over-the-counter yeast product unless you've confirmed it's yeast, because guessing wrong delays the right care. Testing is simple and widely available: a urine cup, a self-collected swab, or a brief exam, often free or low-cost at health departments, Planned Parenthood, and Title X clinics. You can also start by choosing where to get tested.
A BV diagnosis is common, and clinics handle it every day. It's a bacterial balance, and it says nothing about you as a person.