What’s the difference between bacterial vaginosis and thrush?

bv and thrush

Both bacterial vaginosis (BV) and thrush are very common conditions. It’s rare that either is serious, but both can be distressing because of the symptoms they can cause. However, there are many things you can do to reduce your chances of getting them, and treatments for both are very effective.

What causes BV and thrush?

BV is caused by an overgrowth of bacteria that is normally found in the vagina. There are millions of “good bacteria” in the vagina, and the bacteria that causes BV (ironically, also a “good bacteria”) is kept in check (ie. there are not an excessive number of them) because there are other bacteria called lactobacilli, also found in the vagina, which compete for space and food.

When the environment in the vagina is altered (becomes too acidic, for example), the number of lactobacilli decreases and the good bacteria have more space to grow, and so the mix of bacteria in the vagina is disrupted. The good bacteria are anaerobic, meaning they thrive on an airless environment. When this set of bacteria overgrows, the environment in the vagina becomes less acidic than usual, which makes it even more likely for anaerobic bacteria to thrive and lactobacilli to decrease in number.

It is unknown what causes the bacterial balance to be disrupted in the first place. What is known is that if the environment is more acidic it allows the anaerobic bacteria to overgrow. It is not caused by poor hygiene — in fact, using perfumed soaps, bubble bath, vaginal deodorants, and antiseptic liquids in baths actually changes the acidity of the vagina and increases your chances of getting BV.

BV is caused by an overgrowth of bacteria that is normally found in the vagina. There are millions of “good bacteria” in the vagina, and the bacteria that causes BV (ironically, also a “good bacteria”) is kept in check because there are other bacteria called lactobacilli, also found in the vagina, which compete for space and food.

Thrush is also caused by an overgrowth of normal organisms which live in the vagina, but instead of bacteria it is an overgrowth of Candida yeast. Just like BV, when the vaginal environment changes, Candida yeast has a chance to overgrow and it is at this time that it causes problems and is known as thrush.

Situations when this may happen include taking antibiotics. Antibiotics reduce the good bacteria in the vagina, which means that Candida has more food and space to grow.

What are the differences between symptoms of BV and of thrush?

Both BV and thrush can present with vaginal discharge. In BV, the discharge is often white-grey in colour, watery, and has a fishy smell. This smell may be more noticeable during intercourse or after menstruation. The discharge is not usually associated with significant itching or discomfort around the vagina or vulva (opening of the vagina). There may also be a burning sensation when you pee.

Symptoms usually last two to three days if treated with antibiotics. Many women with bacterial vaginosis have no signs or symptoms at all and if it is not causing any problems it may not need treatment.

In thrush, the vaginal discharge is thick, creamy white, curd-like, and does not have a smell. Unlike BV, the vaginal discharge is often associated with intense itching, redness, discomfort or pain around the vagina or vulva. If the itching is intense this is more likely to be due to thrush rather than bacterial vaginosis. There may be an associated burning sensation on peeing or having sex. Some women may not have any signs or symptoms and it may be picked up on a routine cervical smear test.

For thrush, there may even just be itching with no vaginal discharge at all, but in BV the main symptom is vaginal discharge. Similarly, if there is redness around the vagina that is severe, this is more likely to be thrush rather than BV.

Do other conditions cause similar symptoms to thrush and BV?

The symptoms of vaginal discharge may be something else if you have other symptoms such as abnormal periods, abdominal pain, you are pregnant, or where sexually transmitted infections (STIs) may be a possibility.

STIs such as chlamydia and gonorrhoea can present like thrush, with vaginal itching and discharge, although the discharge in these instances can be white, green, or yellow. Having abnormal periods, abdominal pain, and vaginal discharge may be due to pelvic inflammatory disease where there is an infection of uterus, ovaries, Fallopian tubes, or cervix, usually caused by STIs. Thrush, on the other hand, does not normally cause abdominal pain.

If you are in any doubt as to what could be causing your symptoms, or if it is the first time you have had thrush, then go and seek advice from your doctor or GP.

Treatment

Both BV and thrush have effective treatments, but each is treated differently, so it is important to go to the doctor and get checked out if you’re unsure.

If there are no symptoms with BV or you only have mild symptoms (little vaginal discharge), then it is possible for the body to correct itself and you may not even need any treatment. Simple lifestyle measures such as having showers instead of baths, and avoiding using strong detergents or deodorants around the vaginal area can help.

Some people think that applying a thin layer of plain, live yoghurt around the vaginal area can help the symptoms of BV settle more quickly, although there is no strong evidence to support or refute this. If BV is particularly troublesome, has symptoms, or you are pregnant, then treatment is needed. BV can be treated with antibiotics in gel or tablet form.

For thrush, there may even just be itching with no vaginal discharge at all, but in BV the main symptom is vaginal discharge. Similarly, if there is redness around the vagina that is severe, this is more likely to be thrush rather than BV.

One commonly used antibiotic is called metronidazole which is given as a twice a day tablet for five to seven days, or a single high dose. An alternative is tinidazole tablets (another antibiotic). Alcohol shouldn’t be consumed while you are taking either of these antibiotics, and you will need to go and see your GP or a doctor to have them prescribed.

Thrush can be treated by antifungal creams, pessaries, or tablets. Similarly to bacterial vaginosis, the use of yogurt containing probiotics smeared over the vulva has had mixed evidence in trials, and is not proven to be effective. Lifestyle measures to diminish your risk of getting thrush include avoiding wearing tight-fitting underwear, and avoiding perfumed products in the vaginal region to reduce irritation.

Common pessaries and creams that are effective include clotrimazole, miconazole, or fenticonazole. Frequently, one single large dose of clotrimazole inserted as a pessary into the vagina may be sufficient to treat thrush. The cream form can be applied around the vulva or a few days, which is good for itching and is safe in pregnant and breastfeeding women.

Anti-fungal treatments that are available as tablets include fluconazole (single dose) and itraconazole (two doses in one day). These treatments are available from your GP, or you can buy fluconazole from the pharmacy without a prescription.

If you do treat yourself and the symptoms do not clear after treatment, it is important to see a doctor because symptoms may be due to something else, perhaps a different strain of yeast, so you may need an alternative anti-fungal treatment, or you may have an underlying reason for susceptibility to thrush such as poorly controlled diabetes.

Dr. Diana Chiu MBChB (Hons), MRCP, PGCERT (Med Ed), PhD

Diana received her medical degree, with honours, from the University of Manchester. She then went on to receive basic and specialist medical training within the north west of England. She carried out in-depth research in medicine and was awarded a PhD in 2016. Currently, she is finishing her medical training at a large teaching hospital, and one of her greatest interests is medical education. She is an advanced life support instructor and writes regularly for post-graduate examination websites, and also holds a PGCERT in medical education with distinction.

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