On this page

What are the causes of bacterial vaginosis?

woman sat on bed
On this page

What is BV?

Bacterial vaginosis (BV) is a condition that affects the vagina, and sometimes causes a change to the consistency and smell of vaginal discharge.

The vagina has a slightly acidic pH, which helps to maintain the harmonious balance of “good” and “bad” bacteria. When this balance is disrupted, bad bacteria can grow uncontrollably, leading to the symptoms of BV.

Causes of BV

BV happens when there is a change in the natural balance of bacteria in your vagina. It isn’t completely clear why BV happens, however it can be triggered by a change to the pH of your vagina. If the vagina becomes more alkaline, this can cause “good” bacteria (lactobacilli) to die off, allowing “bad” bacteria to thrive.

Risk factors for BV

You’re more likely to experience BV if you:

  • Are sexually active
  • Change your sexual partner
  • Have sex without a condom
  • Use perfumed products around and inside your vagina
  • Regularly have baths with bubble bath or shower gel
  • Wash your underwear with strong detergents or perfumes
  • Have the IUD (copper coil)
  • Smoke

Can sperm cause BV or a bacterial infection?

Semen is alkaline and the vagina is acidic, which means unprotected sex with a male partner may disrupt the natural balance of bacteria within your vagina.

Unprotected sex with a male partner can also lead to STIs like chlamydia, gonorrhoea and HIV, as bacteria and viruses can be carried in semen and pre-cum.

Can sperm cause a bacterial infection?

Maintaining your overall health and practising good feminine hygiene can stop you from developing BV and other conditions affecting the vagina. However, because your vagina cleans itself, you do not need to use perfumed soaps or antiseptics.

To avoid BV in the future, do the following:

  • Have showers instead of baths
  • Avoid using perfumed soaps or shower gels to wash your genitals
  • Wear cotton underwear
  • Wash your underwear in mild detergents
  • Avoid douching your vagina and using vaginal deodorants

You can also reduce your risk by quitting smoking – this will have numerous other health benefits. For advice about how you can quit smoking visit our stop smoking service page.

Your vaginal discharge

Your vagina cleans itself with the help of discharge, which is secreted throughout your menstrual cycle. You might notice changes to the texture, colour and smell of your discharge across the month – once you know what is normal for you, you’ll be better equipped to notice any significant changes or new symptoms that suggest BV or an infection.

Can I get BV from oral sex?

Oral sex isn’t listed as a specific risk factor for BV by the NHS, but it’s a good idea to avoid oral sex until you’ve had treatment for your symptoms.

Oral sex is known to spread certain STIs which is why you might want to use condoms and dental dams for this type of sexual activity.

Can my partner catch BV from me?

You can spread BV to a female partner during sex, but not a male partner. If you have a same-sex partner and you’re diagnosed with BV, she may need treatment too.

Can BV cause you to bleed?

BV shouldn’t cause any spotting or other types of abnormal bleeding. If you do experience this symptom you should see your GP or a nurse at your local sexual health clinic.

How can I treat BV?

Bacterial vaginosis can be treated very effectively with a course of antibiotics – learn more by reading our article about BV treatment.