Bacterial Vaginosis (BV): Symptoms and Treatment

Bacterial vaginosis (BV) is a common cause of unusual vaginal discharge, caused by a change in the balance of bacteria in the vagina. Its best-known sign is a fishy smell, often stronger after sex, but many women with BV notice nothing at all. It is not usually serious, it is treated with antibiotics from a GP or sexual health clinic, and it often comes back.

What is bacterial vaginosis?

The NHS describes BV as a common cause of unusual vaginal discharge, caused by an imbalance of bacteria in the vagina. The CDC's treatment guideline describes it in more detail as the normal, lactic-acid-producing Lactobacillus bacteria being replaced by high concentrations of other bacteria, and calls it the most common cause of vaginal discharge worldwide.

ACOG puts it plainly: BV is not a true infection but an imbalance in the types of normal bacteria that live in the vagina, and anyone can get it, whatever their age or whether they have had vaginal sex.

What are the symptoms of BV?

The NHS lists two main symptoms:

• an unusual discharge with a strong fishy smell, particularly after sex
• a change in the colour and consistency of discharge, such as becoming greyish-white, thin and watery

ACOG adds that the odour may be stronger during your period or after sex, and that the discharge is usually thin and dull grey but may look greenish.

BV does not usually cause soreness or itching, according to the NHS. ACOG says itching is not common, though it can happen if there is a lot of discharge. That is one of the clearer differences from thrush, which is covered in Vaginal Thrush: What the Evidence Actually Says.

And many women have no symptoms at all. The NHS says half of women with BV do not have any symptoms, and the CDC guideline notes that the majority of women with BV were asymptomatic.

Is BV a sexually transmitted infection?

Not officially, but sex plays a part. The NHS says BV is not classed as an STI, but sexual activity can trigger it or pass it on, and that it can be passed to a woman, or anyone with a vagina, during sex.

What causes BV?

Nobody fully knows. The NHS says what causes the change in bacteria is not fully known, but that you are more likely to get BV if:

• you are sexually active (though women who have not had sex can also get it)
• you have had a change of partner
• you have an IUD
• you use perfumed products in or around your vagina

The CDC's list of associations includes a new sex partner, more than one partner, female partners, not using condoms, and douching. These are associations found in research, not a verdict on anyone's choices, and the NHS is clear that women who have never had sex can get BV too.

Does BV matter if it does not bother me?

It can. The NHS says BV increases your risk of getting an STI, possibly because it makes the vagina less acidic and lowers its natural defences. The CDC lists an increased risk of acquiring a range of STIs, including HIV, chlamydia, gonorrhoea and trichomoniasis, as well as complications after gynaecological surgery and in pregnancy.

In pregnancy, the NHS says there is a small chance of complications such as premature birth or miscarriage, but that BV causes no problems in the majority of pregnancies. If you are pregnant and your discharge changes, it advises speaking to a GP or your midwife.

The CDC guideline recommends treatment for women with symptoms, and for all pregnant women with symptoms. Whether you need treatment without symptoms is a conversation for your doctor or nurse.

How is BV diagnosed and treated?

A GP or sexual health clinic will want to confirm it is BV and rule out an STI. The NHS says they will ask about symptoms, may look at your vagina, and may take a swab of the discharge.

BV is usually treated with antibiotic tablets, gels or creams, prescribed by a GP or sexual health clinic. ACOG names metronidazole and clindamycin as antibiotics used for BV, taken by mouth or put in the vagina as a cream or gel. Which one, and for how long, is your prescriber's decision.

One point where the sources disagree: alcohol with metronidazole. ACOG says do not drink alcohol while taking it. The CDC guideline says avoiding alcohol while taking metronidazole is unnecessary. If this matters to you, ask the pharmacist who dispenses it.

Why does BV keep coming back?

The NHS says it is common for BV to come back, usually within a few months. If you get it more than 4 times in a year, you may be given an antibiotic gel to use in the vagina for a few months to help stop it returning, and a GP or clinic can help work out whether something, such as sex or your period, seems to trigger it.

Should my partner be treated too?

This is where the advice is changing, and the sources do not all say the same thing.

• The NHS says that if your partner is a woman or has a vagina, they may also need treatment.
• The CDC guideline page says routine treatment of sex partners is not recommended, and notes that no studies have tested treating female partners to prevent recurrence.
• ACOG says sex partners should consider getting treatment to lower the risk of BV coming back, and describes treatment for both female and male partners.
• A 2025 randomised trial of women in monogamous relationships with a male partner found that treating the partner as well led to fewer recurrences within 12 weeks: 35% of women in the partner-treatment group had BV come back, compared with 63% when only the woman was treated (Vodstrcil, 2025).

If BV keeps returning, it is worth asking your clinic directly whether partner treatment makes sense for you.

What can I do myself?

The NHS suggests these to ease symptoms and help prevent BV returning:

• use water and plain soap to wash the genital area
• have showers instead of baths
• do not use perfumed soaps, bubble bath, shampoo or shower gel in the bath
• do not use vaginal deodorants, washes or douches
• do not put antiseptic liquids in the bath
• do not use strong detergents to wash underwear
• do not smoke

On probiotics: the CDC guideline says no studies support probiotic products as an add-on or replacement treatment for BV. The sources read for this article do not address other popular home remedies.

When should I see a doctor?

The NHS says to see a GP or go to a sexual health clinic if you think you have BV, and that it is especially important to seek treatment if you are pregnant. Many sexual health clinics offer walk-in appointments and get results faster than GP surgeries.

The short version

BV is a common imbalance of vaginal bacteria, and what sets it off is not fully known. The usual sign is thin, greyish discharge with a fishy smell, but half of women with it notice nothing. It is treated with antibiotics from a GP or sexual health clinic, often returns, and can be treated again. Newer evidence suggests treating a male partner may reduce recurrence, so ask about it if BV keeps coming back.

Sources

• NHS, Bacterial vaginosis - what BV is, symptoms, risk factors, STI risk, pregnancy, treatment, recurrence, partner treatment, self-care.
• CDC, Bacterial Vaginosis, STI Treatment Guidelines - definition, asymptomatic BV, associations, complications, who to treat, partners, alcohol, probiotics.
• ACOG, Vaginitis - BV as an imbalance, discharge and odour, antibiotics used, alcohol, partner treatment.
• Vodstrcil et al., 2025, Male-Partner Treatment to Prevent Recurrence of Bacterial Vaginosis (PubMed abstract) - recurrence with and without male-partner treatment.

This article describes what those sources say. It is not medical advice, and it is not a substitute for a doctor, nurse or pharmacist.