Oral thrush, also known as oral candidiasis is a yeast/fungi infection of the genus Candida that develops on the mucous membranes of the mouth.
It is most commonly caused by Candida albicans, but may also be caused by Candida glabrata or Candida tropicalis.
Candidosis or Moniliasis refers to adult oral thrush, while "oral thrush" can refer to both adults and babies.
You can read our article about oral thrush in babies here.
Contents of this article:
Fast facts on oral thrush
Here are some key points about oral thrush. More detail and supporting information is in the main article.
- Oral thrush is a common condition, but for most, it does not cause substantial problems
- Candida cause oral thrush
- Individuals with a reduced immune system are worst affected by oral thrush
- Oral thrush can occur more regularly after chemotherapy or radiotherapy to the head and neck
- Oral thrush is more common in people who are taking steroids, wear dentures or have diabetes
- The most obvious symptom of oral thrush is creamy or white-colored deposits in the mouth
- Treatment of the condition depends on the initial cause
- Drug treatments often include nystatin, amphotericin or miconazole
- Heavy smokers are more likely to have oral thrush.
What is oral thrush?
Oral thrush causes thick white or cream-colored deposits, most commonly on the tongue or inner cheeks.
The lesions can be painful and may bleed slightly when they are scraped. The infected mucosa of the mouth may appear inflamed and red.
Oral thrush is caused by species of Candida fungus.
Oral thrush can sometimes spread to the roof of the mouth and the back of the throat.
For the majority of us, oral thrush does not cause any serious problem. However, this is not the case for individuals with a weakened immune system, whose signs and symptoms may be much more severe.
People with poorly controlled diabetes, those taking steroids (especially long-term), as well as individuals who wear dentures have a higher risk of developing oral thrush with more severe symptoms.
Long-term antibiotic therapy can increase the risk of developing oral thrush. Some medications, especially those that dry out the mouth can cause oral thrush to develop. The National Health Service (NHS), UK, mentions that oral thrush is more common among patients who receive chemotherapy or radiotherapy to the head and neck.
The outcome for oral thrush is generally very good. Most people respond well to treatment. However, oral thrush tends to reappear, especially if the causal factor (smoking, for instance) is not removed.
Causes of oral thrush
Tiny quantities of Candida fungus exist in various parts of our body, including the digestive system, skin and mouth, causing virtually no problems to healthy individuals. In fact, C. albicans is carried in the mouths of 35 - 50% of the world's population.
However, people on certain medications, reduced immune systems and certain conditions/illnesses are susceptible to oral thrush when C. albicans can get out of control.
Risk factors for oral thrush
Adult oral thrush is more likely to become a problem for the following groups of people:
- People who wear dentures - especially if they are not kept clean, do not fit properly, or are not taken out before going to sleep
- Antibiotics - people who are on antibiotics have a higher risk of developing oral thrush. Antibiotics may destroy the bacteria that prevent the Candida from reproducing out of control
- Excessive mouthwash use - individuals who overuse antibacterial mouthwashes may also destroy bacteria which keep Candida at bay, thus increasing the risk of developing oral thrush
- Steroid medication - long-term use of steroid medication can increase the risk of oral thrush
- Weakened immune system - people with weakened immune systems are more likely to develop oral thrush
- Diabetes - people with diabetes, especially if it is poorly controlled, are more likely to have oral thrush
- Dry mouth - people with less than normal saliva (xerostomia) are more prone to oral thrush
- Diet - malnutrition, whether caused by poor diet or a disease that hinders nutrient absorption, predisposes people to oral thrush. In particular, diets low in iron, vitamin B12 and folic acid appear to affect infection rates
- Smoking - heavy smokers are more at risk, the reasons behind this are unclear.
On the next page, we look at the symptoms, diagnosis and treatment of oral thrush.