Oral thrush is a condition that can be difficult to recognize at first. It is rarely dangerous and not necessarily painful, but can be very unpleasant and greatly affect your quality of life. Oral thrush is caused by types of yeast fungus called Candida that live in the mucous membranes lining your mouth. Its medical name “oral candidiasis” is taken from this fungus. Oral thrush is most often caused by a type of Candida fungus called Candida albicans.
Most people have small amounts of Candida on the mucous linings of their mouth without it causing any noticeable problems. But given the right conditions, the fungus can start reproducing very quickly. This often affects people who have serious diseases, and it can also be a side effect of certain types of treatment.
Oral thrush is visible as a white coating that covers your mouth and throat. Scraping it off with a tongue depressor will reveal inflamed red spots that often bleed slightly as well. Even if they practice good oral hygiene, people who have oral thrush will notice a constant cottony feeling in their mouth. Their sense of taste will also be affected and they may have pain or a burning sensation on their tongue. This can make it more difficult to enjoy eating and drinking. A severe infection can also cause swallowing problems, so some people with oral thrush end up eating less. It can be hard to speak too.
Causes and risk factors
Oral thrush is usually the result of another medical condition or a side effect of medical treatment. It is one of the most common side effects of cancer treatment. Chemotherapy can damage the mucous membranes and weaken the immune system, allowing the fungus to spread more easily. Radiotherapy in the head and neck region also increases the risk of oral thrush. The more intensive the treatment is, the more likely oral thrush is to develop.
Dentures, diabetes and certain medications (e.g. broad-spectrum antibiotics used for several weeks at a time) can also promote the development of oral thrush. Infections are generally more likely to occur if the body and immune system are weakened. This can happen as a result of HIV/AIDS, for instance. Oral thrush can also affect older people who require nursing care, eat very little and are physically very weak overall. People who are fed through a tube are at greater risk too.
Oral thrush usually doesn't have any serious health implications, but it can be very unpleasant. If the fungus spreads to your food pipe, for example, it may cause problems swallowing.
Left untreated, oral thrush can last for months or even years. In rare cases the fungus may move into deeper layers of tissue, reaching the bloodstream and causing life-threatening blood poisoning (septicemia).
If you are at a higher risk of developing oral thrush, it is important to tell your nurse or doctor about any unusual sensations or pain you may feel in your mouth. They could then check your mouth to see whether it is a fungal infection. If they think it might be oral thrush, a sample of the coating can be taken using a sterilized cotton swab and then tested in a laboratory.
In people who have cancer or HIV/AIDS, oral thrush can be discovered earlier by inspecting their mouths regularly. You can also check for abnormalities yourself in the mirror by looking for changes like a white coating or inflamed areas. Family members or caregivers could also help here.
Although there are a number of recommendations for preventing oral thrush, such as good oral hygiene, not enough research has been done in this area yet.
During cancer treatment it can help to take antifungal medicines as a precaution. This also applies to people who have HIV/AIDS. Antifungal medicines – also called antimycotics – are used to treat fungal infections. These medicines slow fungal growth or destroy any fungi present.
People who have a weakened immune system are at risk of fungal infections spreading to the rest of the body. If you notice symptoms, it is a good idea to talk to your doctor. It is also important for nurses and caregivers to look out for signs of oral thrush if they are caring for someone who is at higher risk of getting a fungal infection. Detecting oral thrush early on can help limit its unpleasant effects and avoid further health problems.
Oral thrush can be treated with antimycotics. These are available as drugs that produce either a topical (local) or a systemic (throughout the whole body) effect. Medication that acts in both ways is also an option. The type of medication that is best suited for someone with a weakened immune system will depend on their individual situation.
Clarkson JE, Worthington HV, Eden OB. Interventions for preventing oral candidiasis for patients with cancer receiving treatment. Cochrane Database Syst Rev 2007; (1): CD003807.
Krebsinformationsdienst (KID). Fieber, Entzündungen und Infektionen bei Krebspatienten. February 4, 2011.
Krebsinformationsdienst (KID). Mund- und Zahnpflege bei Krebs. July 15, 2010.
Pankhurst CL. Candidiasis (oropharyngeal). Clin Evid 2013.
Pienaar ED, Young T, Holmes H. Interventions for the prevention and management of oropharyngeal candidiasis associated with HIV infection in adults and children. Cochrane Database Syst Rev 2010; (11): CD003940.
Worthington HV, Clarkson JE, Khalid T, Meyer S, McCabe M. Interventions for treating oral candidiasis for patients with cancer receiving treatment. Cochrane Database Syst Rev 2010; (7): CD001972.
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