Fact sheet: Fungal infection of the mouth in people who have cancer or HIV/AIDS

Oral hygiene and enjoying good food are important for most people. It follows that it can be very unpleasant to have a cottony feeling in your mouth, loss of taste and trouble swallowing. An oral infection by Candida fungus can cause these symptoms. The medical term of this condition is “oral thrush” or “oral candidiasis”. This often affects people who have serious diseases, but it may also be a side effect of some treatments. This fact sheet will explain how people with cancer or HIV/AIDS may develop oral thrush and what options they have for prevention and treatment.

What is oral thrush?

Oral thrush is an infection of yeast fungus in the mouth and throat. It is caused by yeast fungus – called Candida yeast – that settles in the mucous membranes lining the mouth and throat. This gives the condition its name “oral candidiasis”.

Many people have a small amount of this type of fungus on their mucous membranes without any noticeable problems. The most common is Candida albicans. Specific conditions can cause a marked increase in the yeast population, however, which is visible as a white deposit in the mouth and throat region. Rubbing or scraping the white deposit with a wooden instrument will reveal red inflammations that also often bleed slightly. They are sometimes painful and can impair your sense of taste, as well as making it difficult to speak or eat.

This infection does not usually have serious health implications, but it can be very unpleasant for those affected by it. If the fungus spreads to the esophagus, for example, it may cause problems swallowing. Left untreated, oral thrush can last for months or even years. In rare cases the fungi may penetrate deeper layers of tissue, reaching the circulatory system and causing life-threatening blood poisoning (sepsis).

What are the signs of oral thrush?

The mouth is a very sensitive part of the body, and the tongue is a very sensitive sense organ for detecting any changes in our mouth. It is our sense of taste, coupled with our sense of smell, that determines whether eating is an enjoyable experience. And it is through the use of our mouth and language that we stay in touch with others. Despite keeping up a thorough oral hygiene, people who have oral thrush will have a constant cottony feeling in their mouth, will experience changes in their sense of taste, and may have pain or a burning sensation on their tongue. This can make it difficult to enjoy eating and drinking – it feels unpleasant. Severe oral thrush can also make swallowing difficult, which means that some people end up eating less.

Why are people who have cancer or HIV/AIDS more likely to have oral thrush?

Oral thrush is usually caused by another disease or is the side effect of medical treatment. Oral thrush is one of the most common adverse effects of cancer treatment. Chemotherapy can aggravate the mucous membranes and weaken the immune system, which means that the fungus can spread more easily. Radiotherapy done in the head and neck region also makes oral thrush more likely. The risk of developing a fungal infection rises with increasing amount of treatment.

Dentures, diabetes mellitus and some drugs, such as broad spectrum antibiotics used for several weeks can also promote the development of oral thrush. In general, it is easier for a fungal infection to develop if the body and the immune system are weak. This means that it can also affect older people requiring care who eat little and who are generally quite weak, or people who need to be fed through a tube.

How is oral thrush diagnosed?

Because oral thrush is more common in people who have cancer or HIV/AIDS, these problems can be caught early on if they have their mouth inspected regularly. People who are at a higher risk can examine their mouth themselves in the mirror and look for any changes, such as a white deposit or inflammations. Nurses, doctors, dentists or family members may also do this.

If you are at higher risk, it is important to tell your nurse or doctor about unusual sensations or pain that you may have in your mouth or throat. He or she can then check your mouth and throat area to see whether it might be a fungal infection. If it is suspected that you might have it, a sample can be taken using a sterilized cotton swab. This is then taken to a lab for testing.

Are there options for preventing oral thrush?

Oral hygiene

It would be ideal to have effective measures for preventing fungal infections for people who have a higher risk of getting it. There actually are a number of recommendations for prevention, but there has not yet been enough research on them. This means that it is not clear whether, for instance, a particular form of oral hygiene can in fact prevent a fungal infection.

Here is a description of different types of oral hygiene that have been recommended for people who, for example, are having chemotherapy or radiotherapy to prevent oral thrush.

By going to a dentist before having chemotherapy, and especially before any radiotherapy done in the head and neck region, health problems like inflamed gums, for example, can be detected and treated in advance. But it is also a good idea to see a dentist during and after this kind of treatment.

The mucous lining of the mouth can also be harmed by doing chemotherapy or radiotherapy in the head and neck region. This makes it generally more susceptible to inflammation and injury. Deposits and remaining food particles make it easier for inflammations to develop or fungus to grow. These are all reasons to practice oral hygiene thoroughly but also especially carefully during cancer treatment. It may help to have a toothbrush that has soft bristles. Especially when cleaning the spaces between the teeth, for example by using dental floss, it is important to take care to avoid injuring the mucous membrane lining the mouth. Many people also rinse their mouth with special liquids during chemotherapy or radiotherapy.

For people requiring care who eat or drink very little, it is important to keep their mouth hydrated and to regularly offer them something to drink. The mouth will usually be cleaned several times a day and the deposits will be removed. This is done to prevent, among other things, inflammations from developing and fungus from growing.

If you wear dentures, different factors may influence the likelihood of a fungal infection, for example: poor fit, unsmooth surfaces, food particles and especially deposits. This means that it is important to clean the dentures regularly, for example with a toothbrush and a special cleaning solution.

Medications for preventing fungal infection in people who have cancer

During cancer treatment it may help to take antifungal drugs as a precaution. Antifungals – also called antimycotics – are used to treat fungal infections. They slow fungal growth or destroy existing fungus. This aims both to prevent oral thrush as well as to stop the fungus from spreading throughout the entire body. Antifungal drugs can be introduced to the body in different ways. There are

• drugs that have an effect on a limited region (topical) and
• drugs that have an effect on the entire body (systemic).

Hybrid forms also exist. How an antifungal drug will be absorbed by the body, depends on its dosage form and its mechanism of action.

Antifungal drugs are available in different forms: for example as mouthwashes, ointments, lozenges, syrups, tablets or infusions. Trials show that some drugs that affect the entire body can lower the risk of developing a fungal infection. These types of drugs can be taken as capsules, for example, or given as an infusion. There is no evidence of benefit from antifungal drugs that only have an effect limited to the mouth. These topical antifungals are available as ointments and mouthwashes, for example.

Antifungal drugs can also have side effects. They may cause headache, skin rashes, nausea, vomiting or diarrhea. You can read more about the advantages and disadvantages of preventing fungal infection in people who have cancer in the research summary ”Cancer: Can oral fungal infections be prevented during cancer treatment?".

Medications for preventing fungal infection in people who have HIV/AIDS

Oral thrush is a problem that keeps on cropping up for many people who have HIV/AIDS. For this reason the issue of prevention is especially important for them. Fluconazole is the only drug proven to effectively prevent oral thrush for people who have HIV/AIDS. Taking fluconazole tablets can lower the risk of oral thrush. In older trials about half of the people with HIV/AIDS developed a fungal infection without taking any preventative measures. Taking fluconazole regularly reduced the rate to about one third.

But regular use has its disadvantages too. Fluconazole can cause headache, stomach ache and nausea, for example. Taking it for months at a time can also lead to the germs becoming resistant to the antifungal drugs. This may mean that an antifungal drug does not work as well when it needs to be used for treatment. For this reason, the preventative use of fluconazole is only recommended on a case to case basis.

How can oral thrush be treated?

Antifungal drugs are not just taken for prevention: they are mainly used to treat oral thrush. For treatment there are various drugs and dosage forms available, that is, medications that either have only a local effect or that produce an effect throughout the entire body. Combination drugs, which have an effect both in the mouth well as in the rest of the body, may also be an option for treatment. The medications are usually taken over a period of one to two weeks.

The most common side effects of systemic antifungal drugs are temporary problems like headache, skin rash, nausea, bloating and diarrhea. The choice of which drug is the most suitable will depend on the individual situation.

Treating oral thrush in people who have cancer

If someone develops oral thrush during cancer treatment, it can be treated with antifungal drugs. Both topical medications as well as drugs that enter the body through the digestive tract and have an effect throughout the body are options. Drugs that enter the body through the digestive tract are probably more effective than topical drugs. But due to a lack of research in this area, it is not possible to say whether particular products are more effective in treating oral thrush than others.

Treating oral thrush in people who have HIV/AIDS

People who have HIV/AIDS frequently develop oral thrush due to the weakened state of their immune system. This is quite distressing for many of them. Some end up eating very little because of the pain in the mouth region, which can make the body even weaker. There are different drugs used to treat oral thrush, including fluconazole, ketoconazole, itraconazole and clotrimazole. Fluconazole and ketoconazole, which are absorbed by the digestive tract, were shown to be more effective in trials than nystatin, which is used topically.

Dealing with the risk of developing oral thrush

Fungal infection of the mouth is a condition that might go unnoticed if you are not careful. It is rarely dangerous and possibly painless, but it is very unpleasant for the person it is affecting and can greatly reduce quality of life. Also, people who have a weakened immune system are at risk of the fungal infection spreading to the rest of the body. So it is important for people who are at a higher risk to know that they may develop oral thrush and to be aware of what options are available for prevention and treatment. If there are possible signs of the condition, it does make sense to talk to a doctor about it. It is also important for people who are caring for someone who is at a higher risk of getting a fungal infection to pay extra attention, to help with prevention, and to look for signs of oral thrush. Detecting oral thrush early on can help limit its unpleasant effects and possibly avoid further health problems.

Author: Institute for Quality and Efficiency in Health Care (IQWiG)


Next planned update: April 2015. You can find out more about how our health information is updated in our text "Informed Health Online: How our information is produced".

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