Oral Thrush

What is oral thrush?

Oral thrush is a fungal infection that occurs in your mouth, throat, tongue and oesophagus (the long, muscular tube that travels from the back of your mouth down to your stomach)[4]. It occurs when a species of fungus that lives naturally in your mouth and digestive system, called Candida albicans, overgrows.

Candida albicans is normally prevented from overgrowing by your immune system, which works to keep your balance of healthy to bad bacteria in check[5]. However, certain things can disrupt the maintenance of this healthy balance and cause you to develop oral thrush.

Many types of the Candida fungus also live naturally in other parts of your body, such as the vagina, penis and in the folds of your skin[6]. As a result, there are different types of thrush depending on the location of the infection in your body and the species of Candida at work[7]. If you’re looking for thrush treatments for other parts of the body, you can find them in the general thrush page.

Is oral thrush contagious?

No, oral thrush is not contagious. This is because most people already have Candida albicans living in their mouth. So, as long as their immune system is doing its job and defending their mouth and digestive system from an overgrowth of the bacteria, the infection cannot be passed on.

Oral thrush symptoms

The symptoms of oral thrush usually come on suddenly, and include[8]:

•       Creamy, white, slightly raised patches in your mouth. These are usually on your tongue and inner cheeks, but sometimes develop on your gums, tonsils, the roof of your mouth and at the back of your throat
•       Slight bleeding if the patches are rubbed or scraped
•       Redness, burning and soreness that may make it difficult to eat and drink
•       A loss of taste
•       Cracking and redness at the corners of your mouth
•       A cottony feeling in your mouth

In severe cases, usually related to a weakened immune system from cancer treatment or HIV/AIDS, the white patches can spread into your oesophagus. This is called Candida oesophagitis. If this occurs, you may have trouble swallowing due to pain or feel as if food is getting stuck in your throat or mid-chest area. You may also develop a fever if the infection spreads beyond your oesophagus.

If you’re looking for oral thrush pictures to help you identify whether you or your baby may have the infection, you can find some on the NHS website.

How is thrush diagnosed?

Your GP will usually be able to diagnose oral thrush with a visual examination of your mouth[9]. They will look for the distinctive white patches on your tongue and inner cheeks that bleed slightly when lightly brushed away.  

Before making a diagnosis, your GP may take a small scraping of the fungus to be examined under a microscope for Candida albicans.

If they suspect the thrush extends into your oesophagus, they may also recommend:

•       An endoscopy – an endoscope (a lighted, flexible tube with a camera on the tip) is used to examine your oesophagus, stomach and the upper part of your small intestine
•       A biopsy – if an endoscopy indicates thrush or more unusual findings, they may take a tissue sample at the same time. This will be sent to a lab to identify which bacteria or fungi are causing your symptoms
•       Blood tests – to assess whether other conditions—such as diabetes and nutritional deficiencies—may be exacerbating your oral thrush

What causes oral thrush?

Factors that can disrupt the balance between your good bacteria and the Candida species of fungus include:

•       Cancer – cancer treatments weaken the immune system and make it more difficult for your body to fight off the infection
•       Diabetes – if you have diabetes that isn’t well controlled, your saliva may contain high sugar levels which encourage Candida to grow
•       Stress – being consistently stressed for a long period of time can weaken your immune system
•       Diets high in carbohydrates and sugar – research has identified that certain sugars and carbohydrates contribute to yeast growth
•       Taking antibiotics – antibiotics disturb the natural balance of bacteria in your body, which can enable Candida to grow out of control
•       Corticosteroid inhalers – inhalers that contain corticosteroids can weaken your immune system in your mouth and throat
•       A weakened immune system – health conditions, such as HIV/AIDS, can weaken your immune system
•       Dentures – dentures provide a microenvironment that encourages the growth of Candida, particularly in people with poor oral hygiene
•       Smoking – rates of oral thrush are higher in smokers, though we don’t yet have a clear understanding of what causes this link
•       Having a dry mouth – as saliva contains antifungal proteins, if you have a dry mouth you have less of these protective proteins

How to treat oral thrush

Oral thrush is primarily treated with antifungal medicines[10]. The antifungal medicine most used to treat oral thrush is fluconazole. It can also be used as a preventative medicine, if you have[11]:

•       Recurrent oral thrush
•       A weakened immune system
•       HIV/AIDS

Fluconazole comes in the form of[12]:

•       Liquids and gels – applied directly inside your mouth
•       Tablets or capsules – taken orally
•       Injection – for severe infections only

Fluconazole usually treats thrush within seven days, though it may take one to two weeks to completely clear up severe thrush. No matter how severe your infection is, you should always finish your full course of fluconazole to prevent it from coming back.

Fluconazole can cause:

•       Nausea
•       Diarrhoea

How to prevent oral thrush

People with lower levels of overall oral health have higher levels of oral thrush[13]. Currently, the cause of this link isn’t clear. However, it’s suggested that maintaining good oral hygiene can help to prevent oral thrush infections.

Steps you can take to promote good oral hygiene include:

•       Brushing your teeth twice a day with a toothpaste that contains fluoride
•       Flossing regularly
•       Rinsing your mouth with water after meals
•       Quitting smoking
•       Going for regular check-ups with your dentist (even if you wear dentures or have no natural teeth, especially if your dentures don’t fit properly)
•       Removing your dentures every night, cleaning them and soaking them in a solution of water and denture-cleaning tablets
•       If you have few or no natural teeth, brushing your gums, tongue and inside your mouth with a soft brush twice a day
•       If you use a corticosteroid inhaler, using a spacer (a plastic cylinder that attaches to the inhaler) when you take your medicine and rinsing your mouth with water after using it
•       Keeping any underlying conditions that can affect your oral health, such as diabetes, under control

Sources

1. https://www.ncbi.nlm.nih.gov/books/NBK367586/
2. https://www.nhsinform.scot/illnesses-and-conditions/infections-and-poisoning/oral-thrush-in-adults/
3. https://cks.nice.org.uk/topics/candida-oral/background-information/prevalence/#:~:text=30–45%25%20in%20healthy%20adults,debilitated%2C%20older%20people%20are%20affected.
4. https://my.clevelandclinic.org/health/diseases/23198-candidiasis
5. https://www.mayoclinic.org/diseases-conditions/oral-thrush/symptoms-causes/syc-20353533
6. https://www.nhs.uk/conditions/thrush-in-men-and-women/
7. https://my.clevelandclinic.org/health/diseases/23199-male-yeast-infection
8. https://my.clevelandclinic.org/health/diseases/10956-thrush
9. https://www.ncbi.nlm.nih.gov/books/NBK546247/
10. https://www.nhs.uk/conditions/oral-thrush-mouth-thrush/
11. https://www.nhs.uk/medicines/fluconazole/about-fluconazole/
12. https://www.nhs.uk/conditions/antifungal-medicines/
13. https://pmc.ncbi.nlm.nih.gov/articles/PMC4429411/