Oral candidiasis (thrush)
- Oral pathology
Candida overgrows when the mouth's defences fall: in babies, denture wearers, after antibiotics or inhaled steroids, with dry mouth, diabetes or HIV.
What it is
Oral candidiasis is an opportunistic infection, usually by Candida albicans, which lives harmlessly in many mouths. Pseudomembranous candidiasis (thrush) shows creamy white plaques that wipe off to leave a red base. Erythematous (atrophic) candidiasis gives red, sore areas, often on the palate under a denture or on the tongue after antibiotics. Angular cheilitis (cracks at the corners of the mouth) and chronic hyperplastic candidiasis are other forms. Candidiasis in an adult without an obvious local cause is a marker of immunosuppression.
How to recognise it
- Local causes: dentures (especially worn at night), inhaled corticosteroids without rinsing, dry mouth, smoking, broad-spectrum antibiotics.
- Systemic causes: infancy, old age, diabetes, HIV, chemotherapy, corticosteroids, iron or B12 deficiency.
- Denture stomatitis: red palate exactly under the denture, often painless.
- Oesophageal candidiasis (odynophagia) in an adult is an AIDS-defining illness.
- Diagnosis is clinical; a smear or culture helps when it does not respond.
Differential and risks
- Unexplained thrush in a young adult: offer an HIV test and check glucose.
- Thrush that persists despite treatment may be resistant Candida, or a non-wiping lesion that needs biopsy.
- Breastfed babies with thrush and a mother with nipple pain need both treated at the same time.
Next step / Initial management
- Treat with a topical antifungal (nystatin suspension or a clotrimazole or miconazole oral form) and correct the cause; rinse after inhaled steroids.
- Dentures: remove at night, clean and soak them, and treat the denture as well as the mouth.
- Extensive, recurrent or oesophageal disease, or immunosuppression: systemic fluconazole and investigation (HIV test, glucose, blood count); check drug interactions of azoles.
- No response after a full course or a non-wiping plaque: refer for assessment and biopsy.
Test yourself
Think of the answer, then tap the question to see it.
What simple advice prevents candidiasis from inhaled corticosteroids?
Rinse the mouth with water and spit after each use (and use a spacer).
Where does denture stomatitis appear?
On the palate exactly under the upper denture, usually as painless redness.
What does oral thrush without a local cause in a young adult suggest?
Immunosuppression, especially HIV infection, or diabetes.
Connections
In Pharmacology4
Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.
Sources: Oral Candidiasis (StatPearls Publishing (NCBI Bookshelf), 2023); Fungal Infections of the Oral Mucosa (StatPearls Publishing (NCBI Bookshelf), 2026); Thrush - children and adults (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.