Oral thrush



  • Fungal infections may occur all over the body.
  • Fungal infection of the mouth – oral thrush – is usually caused by Candida albicans.
  • Some people are more susceptible to fungal infections than others.
  • Oral thrush is common in babies, young children, people with AIDS and the elderly.
  • Some people may be carriers of fungi, but are symptom free.
  • If left untreated, fungal infections may cause discomfort and pain.


Yeasts and fungi thrive in warm, moist conditions.

Candida albicans is a yeast that everyone has in the gut. Under certain conditions it invades the skin or mucous membranes. When it affects the mouth, it is called oral thrush.

Fungi can be passed on quite easily from one person to another, but this does not mean that the fungus will necessarily infect the other person. Some people are more susceptible to fungal infections. In these people the presence of fungi on the body will result in fungal infections.

Fungi can live on people, objects or animals for several months.


The yeast Candida albicans causes thrush. Babies with thrush usually contract the infection during delivery, when they pass through a vagina infected with yeast. Symptoms appear as oral thrush within seven to 10 days after birth.

Thrush may ocassionally develop after a viral upper-respiratory infection or infectious mononucleosis (glandular fever). However, the most common predisposing factors to developing oral thrush are AIDS, antibiotic treatment, using steroids or other immunosuppressive drugs, or cancer.

The condition may occur after treatment with antibiotics. During treatment with antibiotics, the antibiotics kill all the normal bacteria in the mouth, giving the Candida yeasts the opportunity to flourish. Patients with AIDS, using steroids, or with chronic debilitating illnesses such as cancer have a suppressed immune system, which allows the yeasts to cause an infection in the mouth (or indeed in other areas of the body as well).


  • Curd-like white patches inside the mouth, on the tongue, palate and around the lips
  • Red, inflamed areas underneath the white surface, with slight bleeding when attempting to scrape off the white patches
  • Cracked, red, moist areas of skin at the corners of the mouth
  • Fussiness, irritability, and poor feeding in infants if the infection is painful (rare)


Thrush is a very common condition in patients with risk factors (i.e. impaired immunity), although the actual prevalence is difficult to calculate accurately. It is certsainly recognised as a very common opportunistic infection in patients with AIDS.


Thrush may recur often in people with chronic illnesses and those with impaired immunity. Candida albicans may also spread to other parts of the body, such as the oesophagus, causing Candida oesophagitis.

Risk Factors

  • Susceptibility to fungal infection or previous fungal infection
  • Impaired immune system owing to illnesses such as diabetes, cancer or Aids
  • Newborn babies
  • People using antibiotic medication
  • The chronically ill (such as diabetics)
  • The elderly
  • People using corticosteroid drugs or other medications that suppress the immune system

When to see a doctor

Call your doctor if:

  • Curd-like white patches appear inside the mouth
  • Mouth irritation prevents a baby from feeding
  • In addition to the above, there is difficulty swallowing


Diagnosis is based on a medical history and specific information about:

  • Diabetes
  • HIV
  • Chronic illnesses
  • Recent respiratory infections
  • Infectious mononucleosis (glandular fever)
  • Diet
  • Recent use of antibiotics
  • Recent use of medications that suppress the immune system

In babies the diagnosis may be suggested by the presence of nappy rash, which is caused by the same fungus.

Examining the mouth and scraping the surface of the thrush to see if there is bleeding usually suffice for making the diagnosis. In addition, the following tests may be done:

  • A scraping of the skin, for a fungal culture
  • Blood and other tests, to determine undiagnosed medical conditions such as diabetes, cancer and HIV infection


Home treatment

Home treatment of fungal infections focuses on preventing reinfection and spreading of the infection.


Anti-fungal medications such as nystatin, clotrimazole, ketoconazole and fluconazole are used for treating thrush and in more severe cases, Itraconazole. Nystatin is a suspension that is swished around the mouth and then swallowed. Clotrimazole can be taken in lozenge form. Ketoconazole or fluconazole must be taken orally for seven to 10 days. Gentian violet may be used to paint an infected area.


  • Follow a healthy diet.
  • Use antibiotics only as prescribed by a doctor.
  • Visit the dentist if you have an irritation caused by dentures.
  • Pregnant women should be checked for vaginal thrush to prevent oral thrush infection of their newborn babies.

Reviewed by Dr Andrew Whitelaw, MBBCh (Witwatersrand), MSc (UCT), FCPath (Micro) (SA) Senior registrar, Department of Microbiology, University of Cape Town and Groote Schuur Hospital.

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