Causes Of Thrush

Thrush is a yeast infection. The vagina contains a range of naturally-occurring micro-organisms that work together to keep it healthy. One of these is a fungus called candida albicans, which contains yeast.

While it’s normally present in the vagina without any problems, if the balance of fungi and bacteria changes, candida albicans can multiply rapidly and cause thrush symptoms.

Taking antibiotics

Antibiotics are designed to kill bacteria. Unfortunately, some of the ‘good’ bacteria that are keeping the candida in check can sometimes get caught up in the crossfire. This shifts the balance in favour of the fungi, which leads to thrush symptoms developing.


When you become pregnant, your body undergoes a large hormonal shift. Specifically, you have higher oestrogen levels than normal and this provides candida with the perfect conditions to multiply.

Find out more about how to deal with thrush during pregnancy here.


If your sugar levels are high, this is another environment that candida can thrive in. While having diabetes doesn’t necessarily mean you’ll suffer from regular bouts of thrush, if it’s poorly controlled, it does make the condition more likely.

A weak immune system

Your immune system usually keeps your candida levels at a reasonable level. If it’s weakened for any reason, perhaps because you have a serious illness or you’re undergoing treatment, you lose this layer of security.

Your menstrual cycle

Some women find they are prone to bouts of thrush in the days leading up to their period.

That’s because your period changes the pH balance of your vagina and makes it more acidic.

This is a balance that makes it easier for candida to multiply, but your symptoms will usually settle down once your period starts.

This is one of the reasons why thrush is more common among women in their 20s and 30s.


Stress prompts your body to release cortisol, which can increase your risk of thrush in two ways. It temporarily weakens your immune system and causes a spike in your blood sugar levels, both of which create the ideal environment for candida albicans.

No, but it can sometimes be triggered by sex, in particular having sex when you’re not fully aroused. If this happens, the vaginal dryness can cause irritation that allows thrush to thrive.

In rare cases, thrush can be passed between people during sex, so it’s best to avoid having sex until it has cleared up.

However, as it’s not classed as an STI, there’s no reason to let your current or former partners know about it.

If you have more than four bouts of thrush within 12 months, this is described as persistent thrush.

Sometimes, you can spot a pattern that reveals the cause of this. For example, if thrush always strikes just before your period, you know that this is a time when you need to be prepared.

However, in some cases it may not be clear why your thrush keeps returning. Whatever your situation, you’re doing the right thing by seeking medical advice. Our doctors will help you work out why you’re getting thrush and prescribe effective treatment to deal with the symptoms.

Aside from the ones that clearly only apply to women, most of the causes mentioned above can also be responsible for thrush in men. Antibiotics, a weak immune system, diabetes or stress can all increase your risk.

Another possibility to consider is poor penis hygiene. Candida albicans thrives in warm, moist conditions, so if the penis isn’t cleaned properly, it can provide the ideal conditions for the fungus to multiply.