Oral Thrush: Symptoms, Causes, and Treatment for Fungal Mouth Infections

Oral thrush is a common fungal infection in the mouth, characterized by creamy white lesions, and often signals an underlying health issue.

By Garret Merkley · Explainer · Jun 7, 2026

Branched from How Diabetes Changes Recommended Dental Visit Frequency

Quick take

Oral thrush is a fungal infection caused by an overgrowth of *Candida albicans* in the mouth.
Symptoms include creamy white patches, pain, and sometimes difficulty eating or swallowing.
Risk factors include weakened immune systems, certain medications, and chronic conditions like diabetes.
Treatment involves antifungal medications and addressing any underlying health issues.

Oral thrush, also known as oral candidiasis, is a fungal infection of the mouth and throat. It's caused by an overgrowth of the yeast *Candida albicans*, which is naturally present in small amounts in most people's mouths. When conditions in the mouth or body change, this yeast can multiply excessively, leading to visible symptoms.

How Oral Thrush Develops and What It Looks Like

*Candida albicans* typically lives in harmony with other microorganisms in your mouth. However, certain factors can disrupt this balance, allowing the fungus to grow out of control. This overgrowth leads to the development of creamy white lesions, usually on the tongue and inner cheeks, but they can also spread to the roof of your mouth, gums, tonsils, or the back of your throat.

Common Symptoms of Oral Thrush

Creamy white lesions on your tongue, inner cheeks, roof of your mouth, gums, or tonsils
Slightly raised lesions that may bleed when scraped or rubbed
Redness or soreness inside the mouth
Cracking at the corners of your mouth (cheilosis)
A cottony feeling in your mouth
Loss of taste or an unpleasant taste
Pain during eating or swallowing

Understanding the Causes and Risk Factors

Oral thrush is often a sign that your immune system is compromised or that there's an imbalance in your body's natural flora. While anyone can get it, some individuals are more susceptible:

**Weakened Immune System:** Conditions like HIV/AIDS, cancer, organ transplant, or medications that suppress the immune system (e.g., corticosteroids) significantly increase risk.
**Diabetes:** Uncontrolled diabetes can lead to higher sugar levels in saliva, creating a more favorable environment for *Candida* to thrive.
**Medications:** Antibiotics can kill beneficial bacteria that keep *Candida* in check. Oral corticosteroids (e.g., for asthma) and certain dry mouth medications can also increase risk.
**Denture Wearers:** Poorly fitting dentures or inadequate denture hygiene can create moist, dark areas where fungus can grow.
**Poor Oral Hygiene:** Infrequent brushing and flossing can contribute to the overgrowth of oral microbes.
**Smoking:** Smokers are more prone to oral thrush.
**Infants and Elderly:** Babies have undeveloped immune systems, and the elderly often have weakened immunity, dry mouth, or use dentures, making them more vulnerable.

Treatment and Why It Matters

Treating oral thrush typically involves antifungal medications. These can come in various forms, such as lozenges that dissolve in the mouth, liquids to swish and swallow, or pills for more severe or widespread infections. The specific treatment and duration depend on the severity of the infection and the patient's overall health. Beyond medication, it's crucial to address any underlying causes, such as controlling blood sugar levels for diabetics, improving denture hygiene, or adjusting medication dosages in consultation with a doctor. Ignoring oral thrush can lead to persistent discomfort, difficulty eating, and in immunocompromised individuals, the infection can spread to other parts of the body, such as the esophagus, lungs, or digestive tract, becoming a more serious health concern.

Is oral thrush contagious?

Oral thrush is generally not considered contagious in the way a cold or flu is. While *Candida* can pass between people (e.g., from a mother to a baby during breastfeeding), it usually only causes an infection if the recipient has a weakened immune system or other predisposing factors.

How is oral thrush diagnosed?

A dentist or doctor can usually diagnose oral thrush by simply examining your mouth. They may gently scrape one of the lesions to obtain a sample, which can then be examined under a microscope to confirm the presence of *Candida*.

Can babies get oral thrush?

Yes, oral thrush is very common in infants, especially in the first few months of life. Their immune systems are still developing, making them more susceptible. It often appears as white patches in their mouth and can sometimes be passed to a breastfeeding mother's nipples.

How long does it take to treat oral thrush?

With proper antifungal treatment, symptoms often begin to improve within a few days. A full course of treatment typically lasts 7 to 14 days, though some cases may require longer, especially if there's an underlying medical condition.

What happens if oral thrush is left untreated?

If left untreated, oral thrush can cause ongoing discomfort, pain, and difficulty eating and swallowing. In individuals with severely weakened immune systems, the infection can spread beyond the mouth and esophagus to other parts of the body, leading to more serious, systemic candidiasis.

Sources

Centers for Disease Control and Prevention (CDC)
Mayo Clinic
National Institute of Dental and Craniofacial Research (NIDCR)