Oral Thrush: A Common Fungal Infection of the Mouth

Oral thrush is a common fungal infection caused by a yeast called Candida albicans.

Interestingly, Candida albicans itself isn't the real problem! In fact, 40 to 60% of healthy adults carry this fungus in their mouths and digestive tracts without any symptoms. That’s because when the immune system is functioning well, Candida albicans coexists peacefully with other friendly bacteria and microorganisms, causing no issues.

The trouble starts when the immune system weakens, allowing the yeast to take advantage, overgrow, and trigger an infection known as oral thrush.

Keep reading to discover more about oral thrush, including its risk factors, symptoms to watch for, and effective strategies to restore a healthy oral microbiome.

How Does Candida Albicans Lead to Oral Thrush?

When Candida albicans grows out of control, it forms a thick biofilm—a kind of protective shield that helps it survive and increases its resistance.



As Candida albicans thrives in the mouth, it can trigger hypersensitivity reactions and release toxins, allowing it to penetrate deeper into the mouth's tissues.

In most cases, oral thrush remains confined to the surface lining of the mouth, appearing on areas like the tongue, lips, and inside the cheeks. However, in some cases, especially in older individuals with weakened immune systems, the infection can become more severe, spreading to deeper tissues such as the esophagus and even the lungs.

What Causes Oral Thrush?

Oral thrush doesn’t have one specific cause. Instead, it develops due to underlying factors that weaken the immune system and disrupt the balance of the oral microbiome. This is why older adults are more commonly affected, as immune function naturally declines with age.

Some of the key risk factors include:

• Anything that disrupts the oral microbiome: Factors like overusing antibacterial mouthwashes, inappropriate antibiotic use, or a sugar-rich diet can upset the delicate balance of the oral microbiome. This disruption allows certain yeasts or harmful bacteria to thrive, potentially leading to infections.


• Poor oral hygiene: Skipping regular brushing and flossing gives harmful bacteria and yeasts a chance to grow and form biofilm on the mouth's surface, making them even more aggressive. This is why brushing twice a day and flossing daily is recommended—to keep the biofilm under control and prevent it from building up.


• Smoking: Smoking reduces blood flow to the mouth’s tissues, hindering immune cells from functioning properly.


• Ill-fitting dentures: Candida albicans can survive on non-living surfaces like dentures. In fact, denture wearers are at a higher risk of developing oral thrush.


• Dry mouth: Saliva plays a crucial role in maintaining the balance of the oral microbiome. When saliva production is low, harmful bacteria and yeasts can overgrow, increasing the risk of infections.


• Sugar-rich diet: A diet high in carbohydrates fuels the growth of oral yeast and harmful bacteria.


• HIV infection: People with HIV have weakened immune systems, making them more vulnerable to oral thrush.


• Cancer and its treatment: Individuals with cancer, or those undergoing chemotherapy or radiotherapy, are more prone to oral issues like dry mouth and infections.

Symptoms of Oral Thrush

Oral thrush can present itself in different ways, depending on its form and severity.

In most cases, the lesions stay within the mouth, appearing as noticeable plaques that cover certain areas.

The most common form is called Acute Pseudomembranous Candidiasis, which appears as smooth, thick, creamy-white, or yellow plaques that can be easily wiped away. These plaques can develop on various parts of the mouth, including the tongue, roof of the mouth, gums, and inside the cheeks.

The white substance is a mixture of dead cells, yeast, and inflammatory debris. When wiped off, it often leaves behind red, sore areas that may bleed. These symptoms are usually accompanied by a burning sensation, dry mouth, and changes in taste—often described as a metallic taste.

Oral Thrush Can Become Chronic

When the acute form of oral thrush persists or becomes resistant to treatment, it can develop into Chronic Candidiasis. This chronic form appears as thick, long-lasting, and irregular white patches with a rough surface.

Unlike the acute version, the white plaques of chronic candidiasis cannot be wiped away. This is because the thickening isn’t caused by a buildup of debris, but rather an overproduction of keratin by the underlying cells in response to the infection. This leads to increased tissue thickness, a condition known as hyperplasia. In rare cases, these lesions may even carry the risk of malignant transformation (cancer).

Another form of chronic candidiasis is Candida-associated Angular Cheilitis, which primarily affects the corners of the mouth where the lips meet. This condition often results in soreness, redness, and deep cracks at the corners of the mouth that may extend onto the surrounding skin, causing both discomfort and cosmetic concerns.

Can Oral Thrush Spread to the Body?

In most healthy individuals, oral thrush remains confined to the mouth and clears up within a few days or weeks after treatment and addressing the underlying cause.

However, for some individuals with certain medical conditions, it may take longer to fully resolve. In rare cases, the infection can spread beyond the mouth, leading to serious complications.

The fungal infection may extend to the esophagus, lungs, heart (Candidal Endocarditis), or brain (Candidal Meningitis).



If the fungus enters the bloodstream and spreads throughout the body, it can lead to a life-threatening condition known as Candida Septicemia. In this situation, the body reacts severely to the infection, potentially resulting in organ failure.

Other Oral Conditions That Resemble Candidiasis

Several oral conditions can resemble oral thrush, causing white patches and discomfort. These include leukoplakia, lichen planus, geographic tongue, and traumatic ulcers.

1. Leukoplakia: White or grayish patches that can appear in any area of the mouth. Some may be precancerous.


2. Lichen Planus: Autoimmune condition causing white patches, redness, or sores in the mouth.


3. Geographic Tongue: Tongue with changing map-like patterns, often painless.


4. Traumatic Ulcers:Painful mouth sores from physical injury or irritation. Usually, they heal on their own after removing the trigger.

If you’re in doubt, it’s crucial to consult your dentist for a thorough examination and the appropriate treatment.

How Is Oral Thrush Treated?

Treatment largely depends on the severity of the infection and your overall health.

Most cases are mild and may not require specific treatment, aside from some home remedies.

Your first priority should be to eliminate any risk factors contributing to the infection. This could involve quitting or reducing smoking, avoiding overuse of mouthwashes, cutting back on sugar, addressing dry mouth, and regularly cleaning your dentures if you wear them.

If you think antibiotics or corticosteroids may be contributing to the issue, consult your doctor about the possibility of changing your medication or adjusting the dosage.

Additionally, consider rebalancing your oral microbiome through dietary improvements, better oral hygiene practices, and supporting the friendly bacteria in your mouth.

A simple baking soda rinse can also be beneficial. Mix half a tablespoon of baking soda in a glass of water and rinse several times a day. Many studies have demonstrated its antimicrobial properties, especially against Candida albicans.

When to See Your Dentist

If your symptoms do not improve after 14 days, it’s important to seek professional help. When diagnosed with oral thrush, the primary treatment typically involves applying topical antifungal creams or gels directly to the affected areas. It’s best to apply these medications between meals and ensure they remain in contact with the patches for as long as possible. This treatment usually lasts from one to three weeks.

In more severe cases or if you have an underlying condition, your doctor may recommend antifungal tablets in addition to the topical treatment.

How to Maintain an Optimal Oral Microbiome

Preventing oral thrush begins with maintaining a healthy oral microbiome, which involves strengthening your immune system and promoting beneficial bacteria.

Here are some helpful tips:

• Maintain Good Oral Hygiene: Brush your teeth at least twice a day with a soft toothbrush and floss daily to remove biofilm from the surfaces of your teeth and gums. This biofilm is a primary culprit behind many mouth infections, including cavities, gum disease, and thrush.


• Clean Your Tongue: The tongue can trap plaque and food debris. If not cleaned regularly, a white coating can form, leading to issues like bad breath. Use a toothbrush or, even better, a tongue scraper once a day to keep your tongue clean.


• Monitor Your Overall Health: Medical conditions and medications, such as diabetes, HIV infection, cancer treatments, antibiotics, and corticosteroids, can weaken your immune system and promote Candida albicans overgrowth in your mouth. Remember, your mouth is a window on your body; what happens in your mouth can reflect your overall health, and vice versa.


• Reduce Sugar Intake: Cutting back on sugar can help you stop feeding harmful yeast and bacteria in your mouth. Instead, opt for foods with natural antifungal properties, such as garlic, ginger, olive oil, and onions. Probiotic-rich foods like yogurt, kefir, and cheese can also help reduce the Candida albicans count in the mouth while supporting the good bacteria.


• Avoid Overusing Antibacterial Products: Excessive use of mouthwashes or antimicrobial agents can disrupt your oral microbiome. While they can be beneficial for short-term treatment of gum inflammation or after oral surgery, prolonged use may cause more harm than good.


• Try Oil Pulling: Oil pulling involves swishing oil in your mouth for 15 to 20 minutes. This technique has been shown to significantly reduce bacterial load in the mouth. You can use any oil, but coconut oil or olive oil are particularly effective due to their antifungal properties.