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Thrush is an infection of the mouth caused by a fungus. It usually begins on the tongue and inside of the cheeks, and spread to the roof of the mouth, gums, tonsils, and throat.



Thrush is caused by a fungus. The immune system can normally fight off this fungus but the fungus can grow and spread if the immune system is weakened.


Risk Factors  

Certain situations can weaken the immune system either in the body or locally in the mouth. A weakened immune system increases your risk for thrush. Factors that can weaken your immune system include:

  • Certain medications such as:
    • Corticosteroid inhalers
    • Medications that treat psychiatric conditions
    • Antibiotics
  • Imbalance of healthy microorganisms in the mouth which can be caused by:
    • Wearing dentures
    • Prolonged illness
    • Conditions that cause a dry mouth


In some cases, you may not have symptoms. In those that have symptoms, thrush may cause:

  • White or red patches on the inside of the cheeks or tongue that may or may not come off when rubbed
  • Sore mouth or throat
  • Difficulty swallowing
  • Differences in taste
  • Fissures or cracks in the mouth

Thrush can spread beyond the mouth. Complications include infections that spread to the:

  • Esophagus—the tube that carries food from the mouth to the stomach
  • Urinary tract
  • Whole body—systemic infection causes multiple organ failure and death