Bacterial vaginosis (BV) happens when the normal balance of vaginal bacteria shifts. The typical sign is a thin, greyish discharge with a fishy smell. BV is common, not a sexually transmitted infection, and usually easy to treat.
Bacterial vaginosis (BV) is the most common cause of unusual vaginal discharge in women of reproductive age. It is not a sexually transmitted infection and it is not a hygiene problem; it is an imbalance of the bacteria that normally live in the vagina.
This article explains how to recognise BV, how it differs from thrush, and how it is treated and prevented.
What Causes Bacterial Vaginosis?
A healthy vagina is dominated by lactobacilli, bacteria that keep the environment slightly acidic. In BV, these protective bacteria decrease and other naturally present bacteria overgrow, raising the pH and producing the typical symptoms.
Anything that disturbs this balance can trigger BV: vaginal douching, perfumed washes and bubble baths, a new sexual partner, or simply individual susceptibility. It is more common in sexually active women but can occur without any sexual activity.
Symptoms: What BV Looks and Smells Like
About half of women with BV notice no symptoms at all. When symptoms occur, the classic picture is:
- Thin, watery, grey-white discharge
- A fishy smell, often more noticeable after intercourse
- Little or no itching, soreness or irritation
Strong itching, thick white discharge or pain suggest a different cause, such as thrush. Our guide to discharge colours and what they mean covers the full picture.
BV or Thrush? Telling Them Apart
The two are easy to confuse but behave differently. BV typically causes a thin grey discharge with a fishy odour and minimal irritation. Thrush (a yeast infection) causes a thick, white, cottage-cheese-like discharge with itching and soreness, usually without a strong smell.
The distinction matters because the treatments are different: BV needs antibacterial treatment, thrush needs antifungal treatment. Using the wrong one delays relief, which is why an examination is worthwhile when symptoms are new or unclear.
How BV Is Diagnosed and Treated
Diagnosis is usually straightforward: your doctor assesses the discharge, may measure vaginal pH and examine a sample under the microscope. Testing also rules out infections with similar symptoms.
Treatment is a short course of antibiotics prescribed by your doctor, as tablets or vaginal gel. Symptoms usually settle within a few days. Your partner does not normally need treatment. Because BV can recur, finish the full course even if you feel better sooner.
Why BV Matters in Pregnancy
BV is usually harmless, but in pregnancy it has been linked to a higher chance of early birth in some women, so symptoms during pregnancy should always be assessed and treated. Mention any unusual discharge at your antenatal visits; treatment in pregnancy is safe and effective.
Preventing Recurrence
Recurrence is common, but simple habits protect the vaginal flora:
- Do not douche; the vagina cleans itself
- Wash the external area with water or unperfumed products only
- Avoid perfumed liners, sprays and strongly scented bath products
- Prefer breathable cotton underwear
- Seek review rather than repeated self-treatment if symptoms return
If BV keeps coming back despite these measures, a gynecological assessment can tailor a longer-term plan.
References
This article was prepared with reference to the following independent health sources.
- NHS. Bacterial vaginosis
- NHS. Vaginal discharge
