Oral thrush, also known as oral candidiasis, is a yeast infection in the mouth caused by a type of fungus called Candida albicans. The infection is not contagious, which means it cannot be passed on to others.

As well as oral thrush that occurs in the mouth, there are also several other types of thrush that affect other parts of the body. For example:

• inside the vagina (vaginal thrush)
• the nappy area of babies
• the folds of skin overlapping the nail (cuticles)
• the skin (candidal skin infection)
• the head of the penis

How common is oral thrush?

Oral thrush is a common problem among certain groups of people. It often affects people who wear dentures because it can be difficult to keep dentures clean. Around 7 in 10 people who wear dentures will develop oral thrush at some stage.

Oral thrush can also occur in people with a weakened immune system, such as those with HIV and AIDS. About 9 out of 10 people with AIDS have oral thrush, which can often be severe.

Oral thrush is also common in people with type 1 diabetes and type 2 diabetes. Diabetes is a long-term condition caused by too much glucose in the blood. A recent study has shown that oral thrush is five times more common in people with severe insulin-dependent diabetes (type 1) than the population at large.

Oral thrush can sometimes affect healthy newborn babies. It can be passed on from mother to baby during labour  if the mother has a yeast infection in her vagina. It can also be passed on through breastfeeding if a yeast infection is present.

Outlook

Left untreated, oral thrush can cause soreness and discomfort in the mouth. However, the condition can usually be successfully treated with antifungal medicines. See for more information. Oral thrush treatment

The symptoms of oral thrush can include:

• sore, white patches (plaques) in the mouth that can be wiped off
• a painful, burning sensation on the tongue
• an unpleasant taste in the mouth that can be bitter or salty
• redness and soreness on the inside of the mouth
• cracks at the corners of the mouth (angular cheilitis)
• difficulty swallowing

Dentures

If you wear dentures and you have oral thrush, you may develop sore, red areas in your mouth where the dentures have been. This is known as denture stomatitis and it can make wearing dentures uncomfortable.

When to seek medical advice

You should seek medical advice from your GP if you have any of the symptoms of oral thrush. It is important that oral thrush is treated quickly because if it is left untreated, the symptoms will persist and your mouth will continue to be uncomfortable.

Oral thrush infections are caused by an increase in the levels of Candida albicans fungi that are naturally present in the mouth. This increase may result from:

• the immune system being weakened (immunodeficiency)
• an underlying health condition, such as cancer or HIV
• smoking 
• taking corticosteroid medication
• certain medications that reduce the amount of saliva produced
• an injury in the mouth

Corticosteroids can be used to reduce inflammation (swelling) and to treat a variety of conditions such as:

• some types of cancer 
• arthritis,which is a condition that causes inflammation of the bones and joints 
• eczema which is a long-term skin condition that causes itchy, dry and red cracked skin
• asthma which is a long-term condition that causes the airways of the lungs to become inflamed and swollen

Inhaled corticosteroids are often used to treat asthma. The medicine is breathed in through an inhaler, which allows it to be passed directly into the lungs. Although inhaled corticosteroids cause fewer side effects than other forms of treatment, they can change the acidity levels in the mouth, killing healthy bacteria and causing an imbalance that makes oral thrush more likely to develop.

Risk factors

You are at an increased risk of developing oral thrush if:

• you have diabetes
• you are a certain age (oral thrush is more common in infants and elderly people) 
• you have high blood sugar levels
• you wear dentures that are poorly fitted or not cleaned regularly
• you often take antibiotics (medication used to fight infections)
• you have an iron deficiency or B vitamin deficiency 
• you are having treatment for cancer such as chemotherapy or radiotherapy

• In most cases, your GP will be able to diagnose oral thrush simply by examining the white patches (plaques) in your mouth. However, some tests may also be used to confirm the diagnosis.

  Biopsy

  A  biopsy may be used to confirm a diagnosis of oral thrush. This involves taking a sample of the white patches in your mouth to check for the candida fungus under a microscope.

  The sample may be stained with a type of dye known as a periodic acid-Schiff (PAS). Your GP may also take a swab from the affected area to monitor how the fungus grows over a period of several days.

  Blood test

  When investigating a case of oral thrush, your GP may recommend that you have a blood test. This is because oral thrush is sometimes associated with other conditions, such as diabetes and nutritional deficiencies.

  Oral thrush can be successfully treated using antifungal medicines.

  Antifungal treatments are available in the following forms:

  • tablets
  • lozenges
  • powders
  • creams
  • rinses

  Rinses are useful for people with a dry mouth who are unable to swallow antifungal tablets.

  Antifungal medicines that can be used to treat oral thrush include:

  • fluconazole
  • itraconazole
  • nystatin
  • clotrimazole
  • miconazole
  • econazole
  • ketoconazole

  If you are taking certain antibiotics or corticosteroids that are thought to be causing your oral thrush, the medicine may need to be changed or the dosage reduced.

  Some antifungal medications should not be used if you are pregnant, breastfeeding or taking other medications. Always seek advice from your GP or pharmacist before taking antifungal medicines.

  Side effects

  Possible side effects of antifungal medicines include:

  • nausea (feeling sick)
  • tummy pain
  • diarrhoea 
  • headache
  • indigestion

  If you wear dentures, an antifungal cream can be applied to the affected area of the roof of the mouth and to the bottom of the dentures. Antifungal lozenges are also effective. 

  If the underlying cause of your oral thrush cannot be cured, you may need to continue taking antifungal treatment for a longer period of time.

  The risk of getting oral thrush can be reduced by following the advice outlined below.

  Oral hygiene

  Your chances of getting oral thrush are reduced if you keep your mouth clean and healthy. You can do this by:

  • rinsing your mouth after meals
  • visiting your dentist regularly for check-ups
  • eating a healthy balanced diet with no more than the recommended amount of sugar
  • keeping your dentures clean
  • brushing your teeth twice a day with a toothpaste that contains fluoride
  • flossing regularly
  • using a mouthwash as part of your routine

  Denture hygiene

  If you wear dentures it is important to clean them regularly to help prevent yeast from growing.

  Your dentures should be removed and cleaned every night before you go to bed. They can be cleaned by brushing them with warm, soapy water and scrubbed with a nailbrush on the non-polished side of the dentures.

  Dentures can then be soaked in any liquid that can be used to sterilize babies' bottles. However, products containing bleach should not be used on dentures that contain metal.

  You should visit your dentist to correct dentures that do not fit properly. This can also reduce the risk of oral thrush and soreness underneath the dentures.

  Speak to your dentist for further advice about how to clean your dentures.

  Smoking

  Smoking encourages the yeast in your mouth to grow and increases your chance of getting oral thrush.

  Speak to your GP if you want to give up smoking. Several treatments are available to increase your chance of quitting successfully, and your GP can put you in touch with local support groups and one-to-one counsellors.

  visit www.quit.ie for information

  Corticosteroids

  If you use inhaled corticosteroids as part of your asthma treatment, you can help prevent oral thrush by:

  • rinsing your mouth with water after using your inhaler
  • developing a good technique when you inhale corticosteroids by using a spacer

  A spacer is a small device that looks like a plastic tube. It is attached to your inhaler and can help to get the corticosteroid medicine right into your lungs, minimising the amount of contact that it has with your mouth.