Thrush is a common fungal infection caused by an overgrowth of Candida yeast, most often Candida albicans.

What is thrush?

In everyday health context, thrush usually means a yeast infection on moist surfaces of the body, especially in the mouth (oral thrush) or genitals (for example, “vaginal thrush”). It happens when Candida, which normally lives harmlessly on skin and mucous membranes, grows out of control and irritates the tissue.

There is also a completely different meaning: “thrush” can be a small songbird in the Turdidae family, known for spotted underparts and melodic songs. In medical conversations, though, people almost always mean the fungal infection, not the bird.

Types you’ll hear about

  • Oral thrush (oral candidiasis): white, creamy patches in the mouth or on the tongue that may be painful or bleed slightly when scraped.
  • Vaginal thrush: itching, soreness and discharge in the genital area due to Candida overgrowth (often just called a “yeast infection”).
  • Skin or other moist-area thrush: Candida overgrowth in skin folds or other damp areas, often when the immune system is weak or skin stays moist.

What causes it?

Thrush develops when something disrupts the normal balance of microbes or weakens the body’s defenses, allowing Candida to multiply. Common contributors include:

  • Recent antibiotics, which kill normal bacteria that usually keep Candida in check.
  • Weakened immune system (for example, chemotherapy, serious illness, immune-suppressing drugs).
  • Conditions like diabetes or dry mouth that change the mouth environment.
  • Infancy or older age, when immune defenses are naturally less robust.

Is it serious?

For most otherwise healthy people, thrush is uncomfortable but not dangerous and usually clears with proper antifungal treatment. In people with significantly weakened immune systems, however, Candida can sometimes spread beyond the mouth or skin and become more serious, which needs prompt medical care.

Important: If you think you or someone else might have thrush (white mouth patches, persistent soreness, or genital itching/discharge), it’s best to see a healthcare professional to confirm the diagnosis and get the right treatment.