Thrush is caused by the Candida albicans fungus.
Many people have a small amount of this fungus in their bodies. However, it does not usually cause problems because it is kept under control by the body’s immune system and other harmless bacteria (so-called "good bacteria").
Thrush can develop when the good bacteria in your body (which keeps candida under control) is destroyed. For example, if you are taking antibiotics to treat an infection, the antibiotics will not distinguish between good and bad bacteria, and will fight off both types.
Also, if you are run down and your immune system is weak, the candida fungus that causes thrush may multiply.
Candida tends to grow in warm and moist conditions. Therefore, you may develop thrush if you do not dry your penis carefully after washing.
Using perfumed soaps and shower gels can irritate your penis, making thrush more likely to develop. Candida also thrives on skin that is already damaged.
HIV, diabetes and other conditions
Men who have HIV, diabetes or other conditions that weaken the immune system are more at risk of developing thrush. This is because the infection develops quickly and the weakened immune system is not strong enough to fight it off.
If you have uncontrolled diabetes (usually because you do not realise that you have the condition), you are more likely to develop thrush. Typical signs of diabetes include:
- excessive thirst
- frequently needing to pass urine
- weight loss
See your GP if you have these symptoms, or if you have thrush that keeps recurring (coming back), even after treatment.