When is vaginal discharge a sign of thrush?

Caucasian woman enjoying a mug of hot coffee in the morning.

Many women will be familiar with the symptoms of vaginal thrush, or vulvovaginal candidiasis, a common condition caused by an overgrowth of yeast. A key symptom of thrush is an increase in vaginal discharge, and a change in its appearance. But how can you tell what is normal and what isn’t? And what other conditions can cause a change in your vaginal discharge?

In women, it is normal to have some vaginal discharge after regular periods have started. Vaginal discharge is formed by the normal bacteria that are present in the vagina and vaginal cells, and mucous produced by the vaginal and cervical cells. This is in order to keep the vagina moist, protecting it from trauma and infection. Normal vaginal discharge is white or transparent, thick or thin, has no smell, and is about a teaspoonful a day in amount (although this is variable in different individuals).

The consistency of vaginal discharge is different during different times of the menstrual cycle. Before the egg is released (ovulation) there is a lot of mucous produced so the vaginal discharge is more watery, clear, slippery, and elastic compared with other times. It is often described as being similar to raw egg white. Just before and after a period, the vaginal discharge becomes sticky, is yellow or white in colour, and cloudy rather than clear.

Vaginal discharge may vary in quantity. Women who take the oral contraceptive pill or who are pregnant may find that their vaginal discharge increases, because the higher oestrogen levels stimulate the vaginal cells to produce more secretions. Women who have been through menopause commonly report a reduction in the amount of vaginal discharge due to reduced oestrogen levels.

To help you figure out why your vaginal discharge has changed, the symptoms of thrush are detailed below, followed by explanations of other conditions which could cause you to experience funny looking, or smelling, discharge.

Vaginal thrush

Vaginal thrush is caused by the yeast family named candida, usually Candida albicans. Candida lives harmlessly on the surface of our gut lining, skin, and vagina. The number of candida is kept under control by our immune system and other bacteria present (other bacteria compete with the space so the candida does not overgrow). Sometimes the conditions change and the yeast has the opportunity to overgrow and cause thrush symptoms.

Some situations predispose women to vaginal thrush. This includes if you have diabetes, for example, because that means there is more sugar in the vagina, which encourages the yeast to grow. Thrush can also develop if you have been on a course of antibiotics, as antibiotics kill the ‘good’ bacteria that normally compete with candida for food and space.

How do I know when I’ve got thrush?

The third most common cause of vaginal discharge is thrush, after bacterial vaginosis (BV) and trichomoniasis (both discussed below).1 The vaginal discharge associated with thrush is often described as looking like cottage cheese because it is creamy white and thick, although be aware that it can also be watery and thin. The discharge may be odourless, or it may have a yeasty smell (like fermenting bread or beer).

It is not well-documented why certain women get a ‘typical’ creamy white discharge while in others the discharge is watery and thin. However, it is likely that this is related to the amount of yeast present and the reaction that woman has to the yeast infection — one individual’s response may be to produce copious amounts of mucous, while another person might have less. In women where there is more mucous production and a lot of active yeast then there would be thicker white discharge. If there is more active yeast in a warm environment then there may be more of a yeasty smell, while if there is less yeast and a dry vagina, there may be less of an odour.

There are other associated symptoms with vaginal thrush, such as vaginal itching and feeling sore in or around the outside of the vagina. Women may experience pain or feel uncomfortable during sex, or they may feel a burning sensation when going to pass urine. The vaginal surface may appear red. These symptoms occur because the thrush irritates the vaginal lining causing inflammation, which stimulates pain and itch receptors.

Some women can have vaginal thrush without any vaginal discharge at all. The cause for this may be because the vaginal and cervical cells are not producing a lot of secretions as they may be affected by a lack of or reduction in oestrogen. This could be due to being postmenopausal, or due to stress, or because of chemotherapy, for example. However, the yeast may still cause irritation and inflammation, therefore stimulating itch receptors to cause itching. Therefore vaginal itching with no vaginal discharge is a common presentation of thrush too.

Other causes of vaginal discharge

There are other conditions which can produce symptoms similar to vaginal thrush, and many women may mistake them for thrush. However, there are differences, and often there are differences in the type and smell of discharge produced. If you are experiencing any of the below symptoms, it is advisable to visit your doctor, or a sexual health clinic.

Bacterial vaginosis

Pain on peeing and unusual vaginal discharge may be caused by bacterial vaginosis. This is due to an imbalance of bacterial growth in the vagina. Unlike vaginal thrush, the vaginal discharge is grey, thin, watery, and has a fishy-smelling odour. There is not normally any itching or vaginal irritation. Bacterial vaginosis is not a sexually transmitted disease, it is common, and can be treated with antibiotics.

Trichomoniasis

This is a sexually-transmitted, parasitic disease. There may be vaginal itching and burning while peeing, pain during sex, and your labia may be red and swollen. Unlike vaginal thrush, the discharge smells unpleasant, (it has been described as a ‘rotting meat’ smell), is green or yellow, and frothy.

Chlamydia and gonorrhoea

Unusual vaginal discharge with pelvic pain, pain on peeing, bleeding between periods or after sex, or any combination of these symptoms may be due to chlamydia or gonorrhoea. These are sexually transmitted diseases that can be treated with antibiotics. Unlike vaginal thrush, the discharge is not white and creamy, but yellow. Chlamydia and gonorrhoea can also be symptomless, so it is important to get tested if there is a possibility you could have contracted either.

Genital herpes

Vaginal discharge with associated red blisters or sores around the genitals may be due to genital herpes. This can be transmitted through sex and is a viral infection that responds to anti-viral medications.

If you notice any unusual changes to your vaginal discharge then it is a good idea to seek advice from your GP, practice nurse, or visit the sexual health clinic. They may take a sample of the vaginal discharge, perform a cervical examination, or take a blood sample to test for sexually transmitted diseases, if indicated. If vaginal thrush is present there are effective anti-fungal treatments such as Canesten.

References

  1. Venugopal et al., ‘Epidemiology and clinic-investigative study of organisms causing vaginal discharge’, Indian J Sex Transm Dis, vol. 38, no. 1, 2017, pp. 69-75.

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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