Mouth thrush (oral candidiasis) causes creamy white, slightly raised patches inside your mouth that often look like cottage cheese. These patches typically appear on the tongue, inner cheeks, roof of the mouth, gums, or tonsils. The infection is caused by an overgrowth of a yeast called Candida that naturally lives in your mouth but can multiply out of control when conditions shift in its favor.
What Thrush Looks and Feels Like
The hallmark sign is white patches or spots on the tongue and inner cheeks. These patches are slightly raised, soft, and sore. If you scrape or wipe them off, the tissue underneath is raw, red, and may bleed. The sensation ranges from mild irritation to significant soreness, especially when eating acidic or spicy foods.
Beyond the white patches, thrush can cause a cottony or dry feeling in the mouth, redness and soreness even in areas without visible patches, and difficulty tasting food. Some people notice a persistent unpleasant taste. In more widespread cases, pain can make eating and swallowing uncomfortable enough to affect appetite.
Cracking at the Corners of Your Mouth
Thrush often shows up at the corners of the lips as well, a condition called angular cheilitis. This looks like cracked, red, sometimes crusty skin right where your upper and lower lips meet. The area can bleed, swell, or develop a soggy, lighter-colored appearance. It tends to sting when you open your mouth wide or eat. If you’re getting persistent cracking at the lip corners alongside white patches inside your mouth, a yeast overgrowth is the likely culprit.
Different Forms of Oral Thrush
Not every case of thrush produces the classic white patches. There are a few variations worth knowing about, because they can look quite different from one another.
The most common type is called pseudomembranous candidiasis. This is the version with the white, curd-like plaques that wipe off to reveal red, sometimes bleeding tissue. It’s what most people picture when they hear “thrush.”
A second form, erythematous candidiasis, skips the white patches entirely. Instead, you’ll see smooth, red, raw-looking areas, especially on the tongue. The tongue may lose its normal texture in patches, appearing flat and shiny where the tiny bumps (papillae) have worn away. This type is particularly common after a course of antibiotics and often presents as a sore, red mouth and tongue without any obvious white coating.
A third form, chronic hyperplastic candidiasis, produces thick, tough white plaques on the inner cheeks or tongue that are hard to scrape off, unlike the soft cottage-cheese patches of typical thrush. This type is less common and tends to develop over a longer period.
Symptoms in Babies
Thrush is very common in newborns and infants. The white patches look similar to what adults experience, but babies obviously can’t tell you their mouth hurts. Instead, watch for fussiness during or after feeding, refusing to latch or take a bottle, and general mood changes that seem tied to mealtimes. A baby with thrush may pull away from the breast or bottle repeatedly, then cry. The infection can also pass between a breastfeeding mother and baby, causing sore, red, or itchy nipples in the mother.
When Thrush Spreads to the Throat
If left untreated or if your immune system is weakened, the infection can move from the mouth down into the esophagus. This is called esophageal candidiasis, and the symptoms shift noticeably. You may experience pain when swallowing, difficulty getting food down, chest pain, heartburn, nausea, or abdominal pain. Some people also notice a worsening loss of taste. Esophageal involvement is uncommon in otherwise healthy adults but happens more frequently in people with HIV, those on chemotherapy, or anyone whose immune defenses are significantly suppressed.
Who Gets Thrush and Why
Candida yeast lives in most people’s mouths without causing problems. Thrush develops when something disrupts the balance. The most common triggers include antibiotics (which kill off bacteria that normally keep yeast in check), steroid inhalers for asthma or COPD, a weakened immune system, uncontrolled diabetes, dry mouth, and dentures that don’t fit well.
Steroid inhalers are a particularly common and preventable cause. The steroid residue that settles in your mouth after each puff suppresses local immune defenses, giving yeast an opportunity to grow. Rinsing your mouth with water or brushing your teeth after each use significantly reduces the risk.
HIV infection dramatically increases susceptibility. Research on HIV-positive patients found that 16% of those not receiving antiretroviral therapy had symptomatic oral candidiasis, compared to just 2% of those on treatment. People on effective antiretroviral therapy had rates of severe symptoms similar to those without HIV, which underscores how closely thrush risk tracks with immune function.
How Thrush Is Diagnosed
In most cases, a doctor or dentist can diagnose thrush just by looking at your mouth. The white patches with their characteristic cottage-cheese texture are usually enough. If there’s any doubt, a small scraping of the affected tissue can be placed in a solution that dissolves everything except fungal cells, then examined under a microscope. This confirms the presence of yeast within minutes. In rare or stubborn cases, a culture can be sent to a lab to identify the exact species, which takes longer but helps guide treatment if the infection isn’t responding.
What Treatment Looks Like
Thrush is treated with antifungal medications applied directly inside the mouth. The two most common options are an oral gel and a liquid suspension. Both work by killing the yeast on contact, so you’re typically asked to hold the medication in your mouth as long as possible before swallowing or spitting it out. For babies, a small pea-sized amount is smeared inside the mouth with a clean finger after feeding.
A typical course runs about seven days, though guidelines recommend continuing treatment for at least a couple of days after symptoms disappear to prevent the infection from bouncing back. If signs persist beyond two weeks, your provider will reassess, sometimes switching to a systemic antifungal taken as a pill. Most people notice improvement within a few days of starting treatment, with the white patches gradually shrinking and soreness easing.
For thrush triggered by steroid inhalers or antibiotics, the infection often resolves once the triggering medication is finished or the inhaler technique is corrected. Recurring episodes, especially without an obvious trigger, can sometimes signal an underlying issue with blood sugar control or immune function worth investigating.