Vaginal thrush is caused by the overgrowth of a yeast-like fungus that lives naturally in the vagina.
Most cases of thrush – between 80 and 90% – are due to a type of fungus called Candida albicans.
The rest are due to other types of Candida fungi.
Up to half of women have Candida living naturally in their vagina without it causing any symptoms.
It's thought that there has to be a change in the natural balance of the vagina, which leads to an explosion in the growth of Candida that causes the symptoms of thrush.
This change can be a chemical change, such as when you take antibiotics. Or it can be a hormonal change, for instance, during pregnancy.
What increases your chances of thrush?
Your risk of developing thrush increases if you:
- take antibiotics
- are pregnant
- have diabetes
- have a weakened immune system
Antibiotics
Thrush happens in about a third of women who take antibiotics because antibiotics get rid of the friendly bacteria in the vagina.
Any type of antibiotic can increase your risk of developing thrush. But for you to develop the yeast infection, the Candida fungus must already be present in your vagina.
Pregnancy
If you're pregnant, changes in the levels of female hormones, such as oestrogen, make you more likely to develop thrush and for it to keep coming back.
Diabetes
Diabetes is a long-term condition that's caused by too much glucose in the blood. It's usually kept under control through insulin injections or through your diet.
If you have diabetes that's poorly controlled, i.e. your blood glucose levels go up and down rather than staying stable, you're more likely to develop thrush.
Weakened immune system
Your risk of developing thrush is also increased if your immune system is weakened, for example, when you have an immunosuppressive condition, such as HIV or AIDS, or if you're receiving chemotherapy. This is because in these circumstances your immune system, which usually fights off infection, is unable to control the spread of the Candida fungus.
Now, find out how thrush is diagnosed.
