Oral thrush in adults

Oral thrush is a fungal infection of the mouth. It’s not contagious and is usually successfully treated with antifungal medication.

It’s also called oral candidosis (or candiasis) because it’s caused by a group of yeasts called Candida.

In some cases, the symptoms of oral thrush can make eating and drinking difficult.

If left untreated, the symptoms will often persist and your mouth will continue to feel uncomfortable.

In severe cases that are left untreated, there is also a risk of the infection spreading further into your body, which can be serious.

Your GP will usually be able to diagnose oral thrush simply by examining your mouth. Sometimes they may also recommend blood tests to look for certain conditions associated with oral thrush, such as diabetes and nutritional deficiencies.

What causes oral thrush?

Low numbers of the fungus Candida are naturally found in the mouth and digestive system of most people. They don’t usually cause any problems, but can lead to oral thrush if they multiply.

There are a number of reasons why this may happen, including:

• taking a course of antibiotics, particularly over a long period or at a high dose
• taking inhaled corticosteroid medication for asthma
• wearing dentures (false teeth), particularly if they don’t fit properly
• having poor oral hygiene
• having a dry mouth, either because of a medical condition or a medication you are taking
• smoking
• having chemotherapy or radiotherapy to treat cancer

Babies, young children and elderly people are at a particularly high risk of developing oral thrush, as are people with certain underlying conditions, including diabetes, an iron deficiency or vitamin B12 deficiency, an underactive thyroid (hypothyroidism) and HIV.

As most people already have Candida fungi living in their mouth, oral thrush is not contagious. This means it cannot be passed to others.

Treating oral thrush

Oral thrush can usually be successfully treated with antifungal medicines. These usually come in the form of gels or liquid that you apply directly inside your mouth (topical medication), although tablets or capsules are sometimes used.

Topical medication will usually need to be used several times a day for around 7 to 14 days. Tablet or capsules are usually taken once daily.

These medications don’t often have side effects, although some can cause nausea (feeling sick), vomiting, bloating, abdominal (tummy) pain and diarrhoea.

If antibiotics or corticosteroids are thought to be causing your oral thrush, the medicine – or the way it is delivered – may need to be changed or the dosage reduced.

Preventing oral thrush

There are a number of things you can do to reduce your chances of developing oral thrush.

If you have a condition or are receiving treatment that could put you at a high risk of developing oral thrush, your doctor may recommend taking a course of antifungal medication to prevent this happening.