Oral Thrush Causes, Symptoms and Treatment

Causes, Symptoms and Treatment of Oral Thrush

Show Article Table of Contents

Thrush, candida albicans, x 400
Microsopic view of candida albicans. London Scientific Films/ GettyImages

Oral thrush is caused by a yeast called candida albicans which are present in many other organisms in the mouth. Half the population has candida in their mouths. Under normal circumstances, candida albicans is kept under control by bacteria.


Sometimes the growth of Candida albicans spirals out of control and oral thrush develops. The most common cause is the use of antibiotics. Oral thrush can also be caused by:

  • Long-term use of corticosteroids
  • Immune disorders, such as HIV
  • Diabetes Mellitus
  • Men with long-term illness
  • Men who wear dentures will have candida in their mouths. This usually happens when the dentures do not fit properly and damage the mucous membranes.
  • Small infants can often get it but it is not usually associated with any disease. (Frequent oral thrush should always be investigated in infants to find out cause).

Risk Factors

Many people who develop oral thrush have weakened immune systems, or are immunocompromised. Immunocompromise refers to a state in which a person's immune system is compromised, or more rarely, absent altogether.

People who are immunocompromised are unable to mount adequate responses needed to battle bacteria and viruses. Thus, a person who is immunocompromised is at higher risk for infection with candida, a bacteria that lives in the mouth of 50 percent of all people.

Here are some common causes of immunocompromised:

  • Chemotherapy
  • HIV or AIDS
  • Cancer
  • Diabetes
  • End-stage renal disease (think dialysis)
  • medications (think steroids)
  • pregnancy

Immunosuppression secondary to many of the above causes of immunosuppression is acquired, which means that people aren't initially born immunocompromised but rather develop immunocompromise later in life.

In addition to oral thrush, people who are immunocompromised are prone to being infected with other opportunistic infections. For example, people with AIDS often fall ill with pneumonia secondary to Pneumocystis jiroveci (previously referred to as Pneumocystic carinii).

Signs and Symptoms

Signs and symptoms usually include:

  • White, creamy or yellow raised spots on the surface of the pink mucous membranes in the mouth. Often described as a curd-like or cottage cheese appearance.
  • Spots can be scraped off, leaving a red tender area beneath, which can bleed.
  • Spots are usually only in the mouth but may spread down into the throat and into the cheeks.
  • Uncomfortable but not usually painful. Oral thrush often causes a burning or soreness in the mouth, the throat, or at the corners of the lips.


Diagnosis is usually made through observation or through laboratory sample.


Antifungal medications are used to control the growth of candida albicans in oral thrush. A course of antifungal medication is given from between 5 to 10 days which are taken into the mouth and held as per instruction by the pharmaceutical company.
These antifungal medications include clotrimazole and nystatin.

A single dose medication is available called Diflucan.


Eating can be difficult and uncomfortable. The infection can spread to other parts of the body in some cases. Oral thrush usually responds quickly to treatment.

If oral thrush persists then checks by your doctor will be needed to see if there is an underlying illness that could be causing oral thrush.