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Thrush (Oral Candidiasis)

What is Thrush (oral candidiasis)?

Thrush, medically known as oral candidiasis, is a fungal infection of the mouth caused primarily by the yeast Candida albicans. While Candida species are a normal part of the oral flora, an overgrowth can produce white, creamy patches on the tongue, inner cheeks, gums, palate, or throat. These patches can be painful, bleed when scraped, and may affect taste and swallowing.

Oral thrush is most common in infants, older adults, and people with weakened immune systems, but anyone can develop it under the right circumstances.

Common Causes

Thrush is rarely caused by a single factor; it usually results from a combination of conditions that disturb the natural balance of microorganisms in the mouth.

• Antibiotic use: Broad‑spectrum antibiotics kill beneficial bacteria that normally keep Candida in check.
• Inhaled corticosteroids: Asthma or COPD inhalers, especially when not rinsed out after use, create a moist environment that favors yeast growth.
• Immune suppression: HIV/AIDS, chemotherapy, organ transplantation, or immunosuppressive drugs reduce the body’s ability to control fungal proliferation.
• Diabetes mellitus: Elevated blood sugar levels provide a rich nutrient source for yeast, and dry mouth (xerostomia) often accompanies diabetes.
• Dry mouth (xerostomia): Reduced saliva from Sjögren’s syndrome, medications, or radiation therapy lowers the mouth’s natural cleansing action.
• Wearing dentures: Ill‑fitting dentures or poor denture hygiene create pockets where moisture and debris accumulate.
• Smoking & tobacco use: Irritates oral tissues and changes the microbiome, making colonization easier.
• Neonatal factors: Premature birth, low birth weight, or use of antibiotics in newborns increase risk.
• Hormonal changes: Pregnancy or hormonal contraceptives can alter oral flora.
• Nutritional deficiencies: Low iron, vitamin B12, or folate levels may impair mucosal immunity.

Associated Symptoms

Thrush often presents with a cluster of signs and symptoms that can range from mild to severe.

• White, cottage‑cheese‑like plaques on the tongue, inner cheeks, gums, palate, or throat.
• Redness or soreness underneath the plaques; the patches may bleed when brushed or scraped.
• Soreness or a burning sensation in the mouth or at the corners of the lips (angular cheilitis).
• Difficulty swallowing (dysphagia) or a feeling that food is stuck in the throat.
• Altered taste or a “metallic” taste.
• Dry mouth or cotton‑like feeling.
• Cracking at the corners of the mouth.
• In infants, irritability during feeding and refusal to eat.

When to See a Doctor

Most cases of oral thrush can be managed at home with over‑the‑counter remedies, but you should seek professional care if:

• Symptoms persist for more than seven days despite self‑care.
• You have a fever, chills, or feel generally unwell.
• White patches spread beyond the mouth to the esophagus (painful swallowing, weight loss).
• You’re pregnant, have diabetes, or are immunocompromised (e.g., HIV, cancer treatment).
• Recurrent episodes occur (more than two episodes in six months).
• There is severe pain, bleeding, or difficulty breathing.

Prompt evaluation helps rule out other conditions (e.g., oral leukoplakia, cancer) and prevents complications.

Diagnosis

Healthcare providers usually diagnose oral thrush based on a visual examination, but they may use additional tools to confirm the infection or assess severity.

1. Clinical examination: The clinician looks for characteristic white plaques and may gently scrape them to see if they reveal a red, bleeding surface.
2. Microscopic analysis: A swab of the lesion stained with potassium hydroxide (KOH) can show yeast cells and pseudohyphae under a microscope.
3. Culture: In persistent or atypical cases, the sample may be grown on Sabouraud agar to identify the specific Candida species.
4. Blood tests: For recurrent thrush, doctors may order a CBC, fasting glucose, HbA1c, or HIV screening to uncover underlying systemic issues.
5. Endoscopy: If esophageal involvement is suspected (painful swallowing, odynophagia), an upper GI endoscopy with biopsy may be performed.

Treatment Options

Therapy focuses on eliminating the yeast overgrowth, relieving symptoms, and addressing any underlying risk factors.

Medical Treatments

• Topical antifungals:
  • Nystatin oral suspension (400,000 IU ml⁻¹) – swish 5 ml for 2 minutes, then swallow; usually 4 times daily for 7–14 days.
  • Clotrimazole troches (lozenges) – dissolve slowly in the mouth, 5 times daily.
  • Miconazole oral gel – apply to the affected area 4 times daily.
• Systemic antifungals (for extensive or refractory disease):
  • Fluconazole 100 mg oral tablet once daily for 7–14 days.
  • Itraconazole oral solution 200 mg twice daily (if fluconazole is contraindicated).
  • In severe immunocompromised patients, amphotericin B may be required.
• Adjunctive care: Adjust or temporarily discontinue inhaled steroids, antibiotics, or other medications that may be contributing, after consulting the prescriber.

Home & Lifestyle Measures

• Good oral hygiene: Brush teeth twice daily with a soft‑bristled toothbrush, floss, and use an alcohol‑free fluoride toothpaste.
• Rinse after inhaled steroids: Use a water rinse or a spacer device and then spit out the water.
• Probiotic foods: Yogurt with live cultures or kefir may help restore bacterial balance, though evidence is modest.
• Dietary adjustments: Limit sugary and yeast‑rich foods (candies, breads, beer) while the infection heals.
• Manage dry mouth: Sip water frequently, chew sugar‑free gum, or use saliva substitutes.
• Dental appliance care: Remove dentures at night, clean them thoroughly with a denture brush and mild soap, and soak in a disinfecting solution weekly.
• Smoking cessation: Eliminates a common irritant and improves overall oral health.

Prevention Tips

Many cases of oral thrush are preventable by addressing the underlying risk factors.

• Maintain optimal glycemic control if you have diabetes.
• Use inhaled corticosteroids correctly: shake the inhaler, exhale fully, inhale, hold breath for 10 seconds, then rinse.
• Limit prolonged courses of broad‑spectrum antibiotics; discuss alternatives with your physician.
• Keep dentures clean and remove them nightly.
• Stay hydrated; adequate saliva production is a natural defense.
• Practice regular dental check‑ups and professional cleanings.
• Adopt a balanced diet rich in vegetables, lean protein, and low in refined sugars.
• Consider prophylactic antifungal lozenges for patients undergoing chemotherapy or bone‑marrow transplant, as recommended by oncology teams.

Emergency Warning Signs

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Sources: Mayo Clinic. “Oral thrush.” Mayoclinic.org; CDC. “Candida infections.” CDC.gov; NIH National Institute of Dental and Craniofacial Research. “Oral Candidiasis.” NIDCR; Cleveland Clinic. “Thrush (Oral Candidiasis) – Symptoms, Diagnosis, Treatment.” ClevelandClinic.org; WHO. “Fungal infections – Candida species.” WHO.int.

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