In shortOral thrush is an overgrowth of Candida, normally a harmless resident of the mouth. The classic form shows creamy white plaques that can be wiped away leaving a red, sometimes bleeding surface underneath. Because Candida overgrows when conditions change rather than when it is newly acquired, the crucial question is always what allowed it — inhaled steroids, dry mouth, dentures, antibiotics, or an undiagnosed medical condition.
The distinguishing test, and it is simple
The classic pseudomembranous form produces creamy white plaques resembling curdled milk on the tongue, palate, or inner cheeks. Gently wiping with gauze removes them, leaving a red and sometimes bleeding base. This single feature is what separates it from leukoplakia, which does not wipe off, and from geographic tongue, where the pattern is one of lost surface texture rather than a removable coating.
| Form | Appearance | Typical setting |
|---|
| Pseudomembranous | White plaques that wipe off | Infants, steroid inhaler users, immunosuppression |
| Erythematous (atrophic) | Red, sore, smooth patches, no white | After antibiotics, under dentures |
| Angular cheilitis | Cracked, sore corners of the mouth | Denture wearers, deficiency states |
| Denture stomatitis | Redness matching the denture outline | Night-time denture wear, poor cleaning |
| Median rhomboid glossitis | Red diamond area, mid-dorsal tongue | Inhaler users, smokers |
The red form is the one most often missed. Erythematous candidiasis produces no white plaques at all — only a sore, red, sometimes burning surface — so patients and clinicians alike look for other explanations. A burning tongue with generalised redness after a course of antibiotics, or a red palate exactly matching the outline of an upper denture, is frequently this rather than an allergy, a deficiency, or a mystery.
Why it appeared: the question that actually matters
- Inhaled corticosteroids for asthma or COPD — the single most common cause in otherwise healthy adults, and largely preventable by rinsing the mouth after every dose.
- Broad-spectrum antibiotics, which suppress the bacteria that normally keep Candida in check.
- Dry mouth from medication, dehydration, or reduced salivary function — saliva is a major antifungal defence.
- Dentures, especially worn overnight or inadequately cleaned; the fitting surface is an ideal reservoir.
- Uncontrolled diabetes — recurrent thrush is a recognised presenting sign, and glucose in saliva feeds the organism.
- Immunosuppression from disease or treatment.
- Infancy and old age, at either end of immune competence.
- Smoking, which alters the mucosal surface and the local flora.
Recurrent or unexplained thrush in a healthy-seeming adult should prompt a medical review, not just a repeat prescription. Persistent or repeatedly returning candidiasis without an obvious local cause is a recognised reason to check blood glucose and consider other causes of impaired immunity. Treating the fungus while ignoring what permitted it produces a cycle of temporary clearance and relapse. This page is general information and not a diagnosis.
Treatment: antifungal plus the underlying cause
- Topical antifungal — a gel or suspension held in the mouth, used for the full prescribed course rather than stopping when it looks better, since early cessation is the commonest reason for relapse.
- Systemic antifungal for extensive, resistant, or immunocompromised cases, on prescription.
- Rinse after every inhaler dose and use a spacer — this alone prevents the majority of steroid-related cases.
- Denture protocol: remove at night without exception, clean the fitting surface daily, soak as advised, and have the fit checked. An untreated denture reinfects a treated mouth within days.
- Address dry mouth and review contributing medications with the prescriber.
- Glycaemic control where diabetes is involved, which does more for recurrence than any topical agent.
Special situations
In infants, white plaques inside the mouth are common and generally straightforward, but breastfeeding transmission runs both ways, so mother and baby are usually treated together to avoid a loop. Feeding equipment needs sterilising during the episode. In denture wearers, angular cheilitis at the corners of the mouth frequently accompanies thrush and often signals both fungal involvement and a reduced facial height from worn dentures — which is why the appliance itself, not only the infection, needs assessment. Persistent oral discomfort with dentures also warrants checking for deposits and fit problems rather than assuming fungus alone.
Notes for patients based in Korea
Bring a full list of your current medications and inhalers to the appointment, since the cause is frequently sitting in that list rather than in the mouth. If you wear dentures, bring them — treating the mouth without treating the appliance is the classic reason thrush returns within a fortnight. We are about 30 minutes from Camp Humphreys and consultations are in English. Book an appointment if you have white or red patches that are not settling.
Frequently asked questions
How do I tell thrush from other white patches in the mouth?
The wipe test is the practical distinction. Thrush plaques can be gently wiped away with gauze, leaving a red and sometimes bleeding surface. Leukoplakia does not wipe off, and geographic tongue involves loss of surface texture rather than a removable coating. That said, a persistent white patch should be examined rather than diagnosed at home by wiping.
Why did I get thrush from my asthma inhaler?
Inhaled corticosteroid settles on the mouth lining and locally suppresses the immune response, allowing Candida already present to overgrow. It is the most common cause in otherwise healthy adults and is largely preventable: rinse your mouth with water and spit after every dose, and use a spacer. This does not reduce the medication effect on your airways at all.
Can oral thrush indicate diabetes?
It can. Recurrent or unexplained candidiasis is a recognised reason to check blood glucose, since raised glucose in saliva feeds the organism and impairs the immune response. This is why repeated thrush in a healthy-seeming adult with no inhaler, antibiotic, or denture explanation warrants a medical review rather than simply another antifungal prescription.
Do I need to treat my dentures as well?
Yes, and it is essential rather than optional. The fitting surface of a denture is a reservoir the antifungal barely reaches, so a treated mouth is reinfected within days by an untreated appliance. Remove dentures every night without exception, clean the fitting surface daily, soak as advised, and have the fit reviewed, since a poorly fitting denture also traps organisms.
Is it contagious?
Candida is a normal mouth inhabitant in most people, so this is overgrowth rather than acquisition, and casual transmission between healthy adults is not a practical concern. The exception is breastfeeding, where mother and infant can pass it back and forth, so both are usually treated together and feeding equipment sterilised during the episode.
Why does it keep coming back?
Almost always because the underlying condition remains. The two most frequent reasons are stopping the antifungal early once it looks better, and treating the mouth while leaving the real reservoir or cause in place — an unclean denture, an inhaler used without rinsing, an untreated dry mouth, or uncontrolled blood glucose. Fixing the cause matters more than the agent chosen.