Your Health A-Z

Oral thrush

Thrush is a yeast infection of the mucous membranes of the mouth and tongue.

Alternative names

Candidiasis – oral, oral thrush

What is thrush?

Thrush is a yeast infection of the mucous membranes of the mouth and tongue. Candida normally lives harmlessly in the body but under certain conditions it may multiply out of control. Candida can also cause yeast infection in the vagina.

What causes it?

Thrush is often diagnosed incorrectly. Other harmless non-infectious abnormalities of the tongue such as ‘geographic tongue’ and ‘hairy tongue’ can be confused with thrush. Thrush can occur in healthy individuals but is more common in people who have certain medical conditions or are receiving medical treatment. The condition may occur after treatment with antibiotics prescribed to treat bacterial infection. This can kill off the normal bacteria in the mouth and allow yeast to overgrow. Thrush may occasionally develop after a viral upper-respiratory infection or infectious mononucleosis (glandular fever). Medication that alters the immune system also causes oral thrush. Inhaled corticosteroid given for asthma or oral or intravenous steroids can also cause thrush. Conditions that alter the immune system can also cause thrush. Yeast infections in the mouth, oesophagus and other mucous members are common in people who are infected by HIV. Babies may contract the infection during delivery, when they pass through a vagina infected with yeast, but often acquire it later from feeding bottles. The most common factors to developing oral thrush are Aids, antibiotic treatment, using steroids or other immunosuppressive drugs, or cancer.

What are the symptoms?

  • 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)

How is it diagnosed?

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 for the presence of white patches which cannot be scraped off like milk curds is usually sufficient 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

How is it treated?

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. An old, but effective and cheap treatment is an aqueous (not alcoholic) solution of Gentian violet. For a baby – one drop in each cheek and one on the tongue three times a day will cure this condition.

What is the prognosis?

Thrush in babies is not painful, but may affect feeding if severe.

Thrush that occurs in the mouth in adults can be cured. It may recur often in people with chronic illnesses and those with impaired immunity. In both infants and adults thrush may go out of control in such cases, particularly in those with HIV/Aids. It may then spread to the food pipe (oesophagus) and cause serious swallowing difficulties.

When to call your 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

How can it be prevented?

  • 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.

The information provided in this article was correct at the time of publishing. At Mediclinic we endeavour to provide our patients and readers with accurate and reliable information, which is why we continually review and update our content. However, due to the dynamic nature of clinical information and medicine, some information may from time to time become outdated prior to revision.

In the interest of our patients, in accordance with SA law and our commitment to expertise, Mediclinic cannot subscribe to the practice of online diagnosis. Please consult a medical professional for specific medical advice. If you have any major concerns, please see your doctor for an assessment. If you have any cause for concern, your GP will be able to direct you to the appropriate specialists.