Introduction

Photo of a woman drinking a glass of water (Ingram Publishing / Thinkstock)

Oral thrush is a condition that can be difficult to recognize at first. It's usually harmless and not necessarily painful, but it 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 membranes lining their mouth and it usually doesn’t cause any noticeable problems. But given the right conditions, the fungus can start growing very quickly. This often affects people who have serious diseases, and it can also be a side effect of certain types of treatment.

Symptoms

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 areas 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. That can make it difficult to eat and drink. Severe oral thrush can also affect your ability to swallow or speak.

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 and are generally very weak overall, eat and drink very little or are fed through a tube.

Effects

Oral thrush usually doesn't cause any serious health problems, but it can be very unpleasant. If the fungus spreads to your food pipe, for example, it may cause problems swallowing. Together with the usual symptoms, this may cause people who have oral thrush to eat less and lose weight. That's mostly a problem if they are already weakened by another medical condition or a treatment, or if they also have other problems like nausea or lack of appetite.

Left untreated, oral thrush can last for months or even years. If your immune system is very weak, the fungi may penetrate deeper layers of tissue in rare cases, reaching the circulatory system and causing life-threatening blood poisoning (sepsis).

Diagnosis

If you have a higher risk of developing oral thrush, it's important to tell your doctor or caregiver about any unusual sensations or pain you may feel in your mouth. They could then check to see whether it's 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.

Oral thrush can be discovered earlier in people who have cancer or HIV/AIDS if they have their mouth checked regularly. You can also check your mouth yourself in the mirror by looking for changes like a white coating or inflamed areas. Family members or caregivers could also help here.

Prevention

If you’re healthy, you don’t have to do anything to prevent oral thrush. People who are at higher risk – due to cancer treatment or HIV/AIDS, for instance – can use antifungal drugs called antimycotics. They kill the fungus or slow its growth.

There is a lack of research on whether doing other things can prevent oral thrush. If you'd like to do something more, it would be best to practice good oral hygiene. Probiotics could possibly help prevent fungal infections in older people.

Learn more

Treatment

Oral thrush can be treated with antimycotics. Some of these medications can be applied directly (topically) to the affected mucous membranes in the mouth. Other kinds are swallowed. They then spread through your body (systemic treatment). Small amounts of topically applied medication enter the gastrointestinal tract (stomach and bowel) through saliva. Some of the medication is absorbed there and then also spreads through the body.

Antimycotics that you take by swallowing them are probably less effective than ones that are applied topically. That's what studies involving people who have cancer or HIV/AIDS suggest. But they can also have side effects, including temporary headaches, rashes, nausea, flatulence (wind) and diarrhea.

Factors like your general health and how much the infection has spread will determine which antimycotic is suitable for you. The medications are typically used over a time period of about one to two weeks.

You can also change what you eat so that the mouth sores are less painful – for example, by switching to soft foods, avoiding hot or alcoholic drinks and using honey instead of sugar as a sweetener.

Further information

When people are ill or need medical advice, they usually go to see their family doctor first. Read about how to find the right doctor, how to prepare for the appointment and what to remember.