Thrush is a fungal infection caused by an overgrowth of yeast called Candida, which naturally lives in your mouth, gut, and on your skin. When something disrupts the balance of microorganisms in your mouth, Candida can multiply and produce the hallmark sign: creamy white, slightly raised patches on the tongue or inner cheeks that look like cottage cheese. Thrush is common, treatable, and typically clears up within one to two weeks with antifungal medication.
What Thrush Looks and Feels Like
The white patches are the most recognizable symptom. They usually appear on the tongue or the insides of the cheeks first, but they can spread to the roof of the mouth, gums, tonsils, or the back of the throat. If you scrape or rub these patches, they may bleed slightly, which helps distinguish thrush from other white spots in the mouth.
Beyond the visible patches, thrush can cause a burning or sore feeling serious enough to make eating and swallowing uncomfortable. You might notice cracking and redness at the corners of your mouth, a cottony sensation on your tongue, or a dulled sense of taste. People who wear dentures often feel redness, irritation, and pain under the appliance.
Who Gets Thrush and Why
Candida already lives in most people’s mouths without causing problems. It only becomes an infection when something tips the balance, usually a weakened immune system or a change in the mouth’s environment. Several specific situations raise your risk significantly.
Broad-spectrum antibiotics taken over several weeks are a classic trigger. These medications kill bacteria throughout the body, including the beneficial bacteria in your mouth that normally keep Candida in check. Inhaled corticosteroids used for asthma can have a similar effect if the medication lingers in the mouth (rinsing your mouth after using an inhaler helps prevent this).
Cancer treatment is one of the most common causes. Chemotherapy damages the mucous membranes and weakens the immune system, creating ideal conditions for fungal overgrowth. Radiation therapy targeting the head and neck raises the risk further, and the more intensive the treatment, the more likely thrush becomes. Conditions that suppress immunity, including HIV/AIDS, also make thrush far more likely.
Diabetes promotes Candida growth because elevated sugar levels in saliva feed the yeast. Older adults who are frail, eat or drink very little, or receive tube feeding are also vulnerable. And denture wearers face a particularly high rate of thrush: studies estimate that between 17% and 75% of people who wear dentures develop a form of Candida-related irritation called denture stomatitis.
Thrush in Babies and Breastfeeding
Thrush is very common in newborns and young infants, whose immune systems are still developing. In a baby’s mouth, it looks like white bumps or patches on the gums, tongue, lips, or throat that won’t rub off easily. Babies with thrush may become fussier during feedings because sucking and swallowing hurts, and they sometimes develop a diaper rash at the same time from Candida passing through the digestive tract.
If a breastfeeding baby has oral thrush, the yeast can transfer to the mother’s nipples. Signs of a nipple yeast infection include redness, cracked skin, swelling around the nipples, shooting pain, and itching. Both mother and baby typically need to be treated at the same time to prevent passing the infection back and forth.
How Thrush Is Diagnosed
In most cases, a doctor or dentist can diagnose thrush just by looking at it. The creamy white plaques have a characteristic appearance, and unlike oral hairy leukoplakia (another condition that causes white patches), thrush patches can be scraped off with a tongue depressor. If there’s any doubt, a clinician can take a scraping and examine it under a microscope after applying a chemical solution that dissolves skin cells but leaves fungal structures visible. Fungal culture or biopsy is rarely needed but can confirm the diagnosis in unusual cases.
Treatment and How Long It Takes
The standard treatment is an oral antifungal taken once daily for 7 to 14 days. Most people see improvement within a few days, though finishing the full course is important to prevent the infection from returning. For mild cases, especially in children, a topical option like a medicated mouth rinse or lozenge that dissolves in the mouth may be enough on its own.
If symptoms don’t improve after 14 days, a higher dose or a different antifungal is typically the next step. When thrush makes swallowing difficult or painful, the infection may have spread to the esophagus, which requires a longer treatment course of 14 to 30 days.
Preventing Thrush if You Wear Dentures
Dentures create a warm, moist environment where Candida thrives, especially if the fit is poor or the acrylic material is porous. A few habits make a significant difference. Remove your dentures every night rather than sleeping in them. Clean them daily with a denture-specific solution. Soaking dentures overnight in a dilute chlorhexidine or sodium hypochlorite solution (about 0.25% bleach solution) reduces Candida colonization effectively. Microwave disinfection of dentures has also been shown to work as well as chemical soaking or topical antifungal treatment. If your dentures fit poorly, getting them adjusted or replaced removes one of the main risk factors.
Can Probiotics Help?
A meta-analysis of 12 studies found that taking oral probiotics reduced Candida counts in the mouth, with the strongest evidence coming from randomized controlled trials. The effect appeared largest in denture wearers. That said, the results are modest, and the quality of available research is mixed. Probiotics are not a replacement for antifungal treatment during an active infection, but they may play a supporting role in prevention for people who get thrush repeatedly, particularly those who wear dentures.
Is Thrush Contagious?
Thrush is not contagious in the way a cold or flu is. You won’t catch it from sharing a drink or kissing someone. The yeast responsible already lives in nearly everyone’s mouth. The exception is the breastfeeding cycle described above, where a baby with oral thrush can transfer yeast to a mother’s nipples and vice versa. Outside of that specific situation, thrush develops because of internal changes in your body’s defenses, not because someone else passed it to you.