What does oral thrush look like?

Oral thrush is a fungal infection of the mouth often caused by an overgrowth of Candida albicans. But why do people receiving cancer treatment sometimes develop it? And, is there any way to prevent oral thrush? 

We checked in with Adegbenga Otun, D.D.S., who researches the oral microbiome. Here’s what he wants cancer patients and their caregivers to know. 

Why do some people develop oral thrush?

The oral cavity is home to many microorganisms, including bacteria and yeast. When everything stays in balance there, your mouth remains healthy.  

Unfortunately, that balance can be disrupted by many factors, including:  

• immunosuppression 
• xerostomia (dry mouth) 
• medications 
• autoimmune diseases 
• uncontrolled diabetes 
• poor oral hygiene 
• faulty dental prostheses 
• chemotherapy
• radiation therapy to the head and neck area 

Any of these may result in otherwise small and quiet organisms flourishing and causing disease.  

One of those diseases is an infection caused by yeast — or a type of fungus — called Candida. The most common species in this group is Candida albicans. Others include Candida tropicalis, Candida krusei and Candida glabrata.  

What does oral thrush look like?

 Candida infections of the oral cavity can appear in a variety of ways. But there are four basic types. 

1. White type: This is what people usually think of when they hear the word “thrush.” It’s the most common and well-known presentation. Known as pseudomembranous candidiasis or “florid” thrush, it appears as a white coating or curdish patches on the tongue and other interior surfaces of the mouth. It can usually be wiped off, leaving behind a red surface. 
   
   
2. Red type: This is less common and also known as erythematous candidiasis. The name comes from the Greek word “erythema,” which means red. In long-term denture-wearers, it’s normally seen as a stark red outline on the denture-bearing area. However, erythematous thrush can make the entire inside of the mouth look inflamed in patients who have chronic dry mouth, Sjogren's syndrome, or have received radiation therapy to the head or neck.
   
   
3. Angular cheilitis: Usually seen as redness or cracks at the corner of the mouth, this is often just an extension of a thrush infection in the oral cavity. It’s primarily seen in patients wearing old, worn-out dentures.  
   
   
4. Median rhomboid glossitis: This usually appears as a reddish patch in the middle of the back of the tongue.  

Does oral thrush hurt?

It depends on the person. Some patients report experiencing a foul taste, a bad odor or a burning sensation in their mouths, but not all do.  

Why do some cancer patients develop thrush?

Saliva is a complex fluid that’s critical to maintaining the health of the oral microbiome. So, anything that disrupts the quantity or quality produced can create a shift in disease-causing microorganisms.  

For cancer patients, that could mean long-term use of medications, such as steroids that suppress oral immune defenses, antihypertensives that make the mouth drier, or chemotherapy- or radiation therapy-induced changes to saliva quality.

The pH of the oral cavity becomes more acidic when it’s dry for long periods of time. This favors the growth of Candida. That’s why cancer patients who have had radiation therapy in the head and neck region are very susceptible to repeated Candida infections. 

How can I tell if I have thrush?

You likely have thrush if the white coating or lesion on your tongue or other surfaces of the mouth: 

• appears “curdish,” like cottage cheese, 
• can be easily wiped off, and 
• leaves a reddish erythema behind.  

If the white coating or lesion on your tongue can’t be wiped off, it’s probably something else. The only way to tell for sure is to have a doctor swab the inside of your mouth and submit it for a growth culture.   

If you have a persistently dry mouth, you may be susceptible to thrush. A well-hydrated oral cavity glistens and feels slick to the touch. But it feels sticky and looks different when it’s dry. As the tongue becomes drier, the papillae, or tiny raised projections on its surface, also may become more pronounced. The tongue can even develop cracks or fissures if it’s been dry for a long time. 

How is thrush typically treated?

We have two ways of treating thrush: topically and systemically. 

Topical treatments usually consist of antifungal oral rinses that weaken the cell walls of Candida so that they become leaky and die. Some of these rinses must be spat out after swishing, but others can be swallowed if the fungal infection extends to the back of the throat.   

There are also antifungal pills you can take to treat thrush. This option is viable when oral rinses or lozenges do not clear persistent or recurrent infections. The downside of systemic antifungals is that they have many drug interactions, which can limit their use.  

Are there any other conditions that can mimic thrush?

Yes. Several conditions can mimic oral thrush. These include: 

• frictional keratosis: a persistent, usually isolated, low-grade irritation of the oral mucosa 
• hairy leukoplakia of the tongue: commonly seen in HIV patients  
• lichen planus 
• smoker’s keratosis 

Anything else people should know about oral thrush?

Fungal infections must be managed promptly in patients who are immunocompromised during cancer treatment; these infections can be fatal.  

Is there any way to prevent thrush?

Yes. But it’s more about reducing the risk factors that can lead to it. 

• Use a baking soda mouthwash: Rinsing out your mouth a few times a day with a baking soda solution can help replicate the oral cavity’s normal alkalinity and buffer any acids. 
• Scrub your tongue: When it comes to oral hygiene, caring for your tongue is just as important as caring for your teeth. So, scrub your tongue daily with a toothbrush and use a tongue scraper at least twice a week. As a general rule, any time a brush goes into your mouth, it should also be scrubbing your tongue. 
• Consider changing medications: Some medications can affect the quantity or quality of your saliva. So, if you’re getting repeated oral thrush infections, ask your doctor about medication alternatives. 
• Get proper dental care: Every living thing produces waste that can be used by other organisms to grow. Even tooth decay can change the oral flora so that it creates a welcoming environment for something else. So, have broken or decaying teeth repaired promptly. 
• Replace dentures regularly: Just because you’re still able to wear dentures made for you 20 or 30 years ago doesn’t mean they’re working properly. Dentures are designed to be effective for about five years. So, if you’re wearing dentures older than that, look into having them replaced.  
• Take your dentures out every night: Saliva contains a lot of protective agents, but dentures prevent it from reaching and coating all the surfaces inside your mouth. So, take out your dentures every night and give your oral tissues a break. 
• Disinfect your dentures: Most dentures have a porous surface, so Candida can grow there and cause reinfection. If you develop a Candida infection, don’t forget to disinfect your dentures in a diluted bleach solution before using them again. 

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