Oral thrush (candidiasis)

Oral thrush is an infection in the mouth usually caused by the fungus (yeast) Candida albicans. Oral thrush is also known as candidosis or candidiasis. 

For most people, oral thrush is mild and can be resolved either by changing oral hygiene practices or with the use of topical (locally applied) treatments. In people with reduced immunity, though, thrush can be more troublesome and widespread and may require treatment with intravenous (injected into the vein) or oral medication.

According to the New Zealand Dermatological Society, 50% of people carry Candida in their mouths. It only causes a problem (thrush or candidiasis), however, when the fungus is able to reproduce and invade the moist surfaces of the mouth (called the mucosae), creating inflammation and causing tissue damage.

Oral thrush is more common in babies and older people but there are a number of factors that can make an adult more likely to develop the infection (see below). It may be possible to treat oral thrush by addressing those factors, however you will be able to treat the infection more quickly, and investigate any underlying problems, by consulting your doctor.

Symptoms of oral thrush

Oral thrush is usually quite easy to identify by looking in the mouth. Symptoms may include:

• a white or cream-coloured patch on the tongue, the inside of the cheeks, or the roof of the mouth (red or bleeding tissue may be revealed if the white layer is scraped off)
• red and sore patches on the mucosae, tongue, or roof of mouth (especially in denture wearers)
• pain in the mouth
• red sores and cracks in the corners of the mouth
• fussiness and not feeding well in babies.

In a breastfed baby with oral thrush, the mother may also have symptoms in one or both breasts:

• red, sensitive or itchy nipples
• flaky or shiny skin on the areola (the dark area surrounding the nipples)
• pain in the breast or nipples during or between feeds.

Risk factors for oral thrush

The Candida fungus is kept at bay by a fine balance of conditions in the mouth, including pH and the presence of ‘good bacteria’. When this balance is upset, either through an underlying condition or the use of medications, the Candida is able to grow more quickly and create an infection. Some of the factors that make a person more likely to develop thrush include:

• infancy or older age
• iron or vitamin B deficiency
• ill-fitting, or poorly cleaned dentures 
• smoking
• inhaled corticosteroids (eg for asthma or COPD)
• antibiotics
• diabetes
• dry mouth (xerostomia)
• HIV/AIDS
• chemotherapy or radiotherapy.

Preventing oral thrush

There are some simple steps a person can take to help prevent oral thrush:

• practise good oral hygiene
• eat natural yoghurt or take probiotics (eg acidophilus), particularly if you are taking antibiotics
• rinse the mouth after using inhaled corticosteroid 
• carefully clean dentures every day.

Treatments for oral thrush

The approaches for preventing oral thrush, listed above, also go a long way to treating the infection if it develops. Depending on the age of the person, and any underlying risk factors, other treatments may include:

• warm salt water rinses (half a teaspoon of salt in one cup of water; rinse and spit out: don’t swallow) 
• sterilisation of dummies, bottles and teats
• oral antifungal medication (prescription only).

If you have used these remedies and your oral thrush persists, visit your doctor again for further investigation. Recurrent or persistent thrush may indicate an underlying condition that requires treatment.

Original article prepared by everybody, reviewed by Prof Richard Cannon, Department of Oral Sciences, Otago University, September 2009