Thrush is an extremely common infection that is known scientifically as candidiasis (infection with Candida). Candidiasis has a distinct appearance when it is found on mucous membranes (the soft, moist, pink or red skin found inside your cheeks, covering your palate and inside your vagina and anus). If the mucous membrane is infected with Candida it looks speckled, with white clumps standing out on the darker background. Once, long ago, somebody thought this speckled appearance resembled the markings on a thrush's breast and so the common name was coined. A bird it is not so what is thrush?
Thrush is caused by an overgrowth of Candida, which is a yeast. Yeast is a type of fungus. Like most healthy people, you probably have small amounts of Candida in your mouth, digestive tract, your vagina and on your skin.
Normally you are unaware of its existence and normally it does you no harm it is only when it grows out of control that it causes problems. Candida is one of billions of micro-organisms that share your body, making up what is known as the normal flora in your system.
The relationship between the micro-organisms and the host (you) is vitally important in maintaining an overall balance of power in your favour. As a healthy individual, you provide an environment ideally suited to the harmonious co-existence of these micro-organisms. This includes warmth, shelter, moisture and food.
But what happens if illness or injury strikes the host? If for some reason your health suffers, then the balance of power may swing, allowing a previously harmless micro-organism to change its nature, causing damage or disease in the host. When this happens, the micro-organism is said to behave in a pathogenic (harmful) manner.
There are eight types of Candida known to cause infection in humans. The most common by far is called Candida albicans.