Bacterial vaginosis (BV) is one of the most common causes of unusual vaginal discharge, yet it is often mistaken for a yeast infection. Telling them apart matters, because BV and yeast infections are treated in completely different ways.
What is bacterial vaginosis?
Bacterial vaginosis is an imbalance in the normal bacteria that live in the vagina. A healthy vaginal microbiome is dominated by protective bacteria called lactobacilli, which keep the vagina mildly acidic. In BV, these helpful bacteria decline and other types of bacteria overgrow, shifting the balance. This is why BV is described as a disruption of the vaginal ecosystem rather than an infection caught from one specific germ.
Importantly, BV is not a yeast infection, and it is not classed as a sexually transmitted infection (STI). That said, BV is more common with sexual activity, a new sexual partner, or multiple partners, and research increasingly shows it has a sexual-transmission component. It can also occur in people who have never been sexually active, so having BV is not a sign that anyone did anything wrong.
Bacterial vaginosis symptoms
Many people with BV have no symptoms at all. When symptoms do appear, the most recognisable signs are:
- A thin, grey or white discharge that often coats the vaginal walls
- A distinctive fishy odor, which may be stronger after sex or during your period
- Usually little or no itching and little irritation
That last point is a useful clue. Significant itching, soreness, and a thick white discharge point more toward a yeast infection, while a fishy smell with minimal itching points toward BV. Because symptoms overlap so much, this is a guide to talking with a clinician, not a way to self-diagnose.
BV vs yeast infection: how the symptoms differ
| Feature | Bacterial vaginosis (BV) | Yeast infection |
|---|---|---|
| Discharge | Thin, grey or white | Thick, white, clumpy |
| Odor | Fishy, often worse after sex | Usually little or no odor |
| Itching | Mild or none | Often intense |
| Cause | Bacterial imbalance | Overgrowth of yeast (Candida) |
| Typical treatment | Prescription antibiotics | Antifungal medicine |
For a fuller side-by-side, see yeast infection vs BV. Other conditions, including some STIs and a urinary tract infection, can cause overlapping symptoms too, which is another reason that confirming the diagnosis with a clinician matters more than guessing from a chart.
What causes BV?
The exact trigger is not always clear, but BV reflects anything that disturbs the vaginal microbiome. Factors linked with a higher chance of BV include:
- A new sexual partner or multiple partners
- Douching, which washes away protective bacteria
- Not using condoms
- Naturally having fewer lactobacilli
BV is not caused by poor hygiene, and you cannot "catch it" from toilet seats, swimming pools, or bedding. Because BV has features of a sexually transmitted condition, the question of whether partners need treatment is an active area of research, which we cover below.
How is BV diagnosed?
You cannot reliably diagnose BV at home, because its symptoms overlap so closely with yeast infections, trichomoniasis, and other conditions. A clinician confirms BV with a quick, low-cost assessment that may include:
- Vaginal pH testing. BV typically raises the vaginal pH above 4.5, whereas a yeast infection usually does not.
- A "whiff" test. Adding a drop of potassium hydroxide to a sample can release the characteristic fishy odor.
- Looking at a sample under the microscope for "clue cells" — vaginal cells coated with bacteria — which are a hallmark of BV.
Some clinics also use newer molecular (DNA-based) tests. The point of testing is simple: it makes sure you get the right treatment the first time, instead of treating the wrong condition and delaying relief.
Why bacterial vaginosis matters
BV is common and often mild, but it is worth treating. Having BV can:
- Raise the risk of catching some sexually transmitted infections, including HIV
- Increase the chance of infection after gynaecological procedures
- Be associated with pregnancy complications, such as preterm birth, which is why BV in pregnancy should always be assessed by a clinician
Bacterial vaginosis treatment
BV usually does not clear on its own, and it cannot be reliably treated with over-the-counter products. Bacterial vaginosis treatment normally requires prescription antibiotics from a clinician, most commonly metronidazole or clindamycin, given as tablets or as a vaginal gel or cream. Your clinician will decide which option and how long to use it; we describe these medicines for information only and do not give doses.
It helps to know what to expect from a course. Symptoms often start to ease within a few days, but it is important to finish the full course even if you feel better, and to follow your clinician's advice about alcohol, which can interact with some antibiotics. If your symptoms have not improved after treatment, go back rather than starting another product on your own.
BV often comes back
One of the frustrating features of BV is that it commonly recurs, sometimes within a few months. Recurrence does not mean you did anything wrong. If BV keeps returning, a clinician may suggest a longer or repeat course or a maintenance plan, so recurrent BV is worth a proper medical review rather than repeated self-treatment.
What about treating a partner?
For years, partners were not routinely treated. That guidance is changing. A 2025 randomized trial found that treating the male partners of women with recurrent BV — alongside the woman's own treatment — substantially reduced how often BV came back, and in 2025 some professional bodies began recommending that clinicians consider partner treatment in recurrent cases for the first time. This is still an evolving area, and it does not apply to everyone, so if you have recurrent BV it is worth asking your clinician whether partner treatment makes sense for your situation.
Douching is not a treatment
Douching does not cure BV and can make it worse by stripping away the protective bacteria your vagina needs. The same caution applies to home remedies and unproven products such as boric acid, which should only ever be considered under a clinician's guidance. The vagina is self-cleaning, so washing the vulva gently with water and avoiding scented products is usually enough.
BV, menopause, and hormones
The vaginal environment changes throughout life. Around perimenopause and after menopause, falling estrogen thins and dries vaginal tissue and shifts the microbiome, which can change discharge and raise the risk of irritation and infection. If you notice new symptoms during this stage, see vaginal health after menopause. Treatments such as vaginal moisturizers or low-dose vaginal estrogen are options to discuss with a clinician, alongside any treatment for BV itself.
When to see a clinician
Because BV, yeast infections, and STIs share symptoms, getting the diagnosis wrong can delay the right treatment. See a clinician if you have a new, unusual, or foul-smelling discharge, or if you are unsure what is causing your symptoms. Seek care promptly if you have:
- Fever, pelvic pain, or abdominal pain
- Sores, blisters, or possible exposure to an STI
- Symptoms during pregnancy, or any bleeding
- Symptoms that do not improve after treatment, or BV that keeps coming back
Any new symptoms or bleeding after menopause should always be evaluated. BV is common and very treatable, but the safest path is a proper diagnosis and prescription treatment from a clinician rather than home remedies or douching.
