The Facts

Oral thrush is a yeast infection of the mouth caused by uncontrolled growth of an organism called Candida albicans.

Candida albicans is an organism that normally makes a quiet home for itself on your skin and doesn't bother anyone.

We all carry this organism. It can be found on the skin, in the mouth, in the gastrointestinal tract (gut) and in the vagina.

Occasionally the yeast multiplies uncontrollably, causing pain and inflammation. When this occurs, it is called candidiasis.

It is also known as moniliasis or a yeast infection. This is most common in infants and toddlers. It is usually mild, but may cause complications for people who have weakened immune systems.


You don't "catch" oral thrush; the yeast is already there. A number of factors can increase the chance of the yeast growing out of control. The leading cause of oral thrush is overuse or prolonged use of antibiotics. Babies may contract thrush during birth if the birth parent has a vaginal infection. A person with uncontrolled diabetes may be more susceptible to thrush since the saliva will have high amounts of sugar, which the organism can use as a food source to multiply.

Yeast must compete with various other organisms, many of them bacteria. These bacteria, which live on the skin and in the intestine and vagina, among other places, are harmless but good at fighting off yeast. When we take antibiotics to deal with disease-causing bacteria, we kill the harmless bacteria as well. Yeast, which is unaffected by antibiotics, is no longer controlled by the bacteria and starts to grow and multiply.

Some cancer medications weaken the immune system and can also allow yeast to flourish. Oral thrush most often develops in people with diseases that weaken the immune system, such as cancer and AIDS. Steroids can also change the environment in the mouth, causing the yeast to grow out of control. A common culprit is inhaled corticosteroids – medications used by people with asthma or chronic lung conditions.

People with a history of diabetes, heavy smoking, dry mouth, or long-term irritation resulting from dentures are also more likely to develop oral thrush.

Symptoms and Complications

Oral thrush causes curd-like white patches inside the mouth, on the tongue and palate and around the lips. It may also cause cracked, red, moist areas on skin at the corners of the mouth. Thrush patches may or may not be painful, or cause a loss or change of taste.

Making the Diagnosis

To make a diagnosis, your doctor will first ask you about recent use of antibiotics or medications, which can weaken the immune system. The doctor will also take into consideration any history of diabetes, cancer, HIV, or other chronic diseases.

Candidiasis is easy to identify. Your doctor may suggest an endoscopy (a procedure to examine the digestive tract with a tube that carries a light and a camera) to diagnose candidiasis in the esophagus. You might be prescribed antifungal medication without doing an endoscopy to see if your symptoms improve.

Treatment and Prevention

Candidiasis isn't normally a dangerous condition except in the rare cases when it enters the blood and spreads to vital organs of people with weakened immune systems.

For oral thrush, a suspension of antifungal medication can be swished in the mouth and swallowed. For severe and recurrent cases, antifungal medication taken by mouth or through a vein can be prescribed.

If the oral thrush is caused by the use of inhaled corticosteroids, rinsing your mouth or brushing your teeth after using your inhaler will help prevent the infection. Avoid using mouthwash with alcohol as it may dry out your mouth. For those with dry mouth, taking sips of water or sucking on sugar-free lozenges may help.

When treating oral thrush, it is important to sterilize or replace your toothbrush often during treatment to avoid re-infection. People who wear dentures should clean them regularly and remove them overnight.

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