A white, cottony coating on the tongue or the inside of the cheeks is one of the more common reasons people visit a pharmacy or GP, particularly if it has appeared alongside a sore mouth or a recent course of antibiotics. Oral thrush is usually straightforward to treat once it is recognised, but it can also be a sign that something else, such as a new inhaler, dentures that need attention, or an underlying health condition, needs a closer look.
This general wellbeing guide explains what oral thrush is and what causes it, how to recognise the symptoms, who is more likely to get it, the antifungal treatments a pharmacist or GP may recommend, how to reduce your risk if you use a steroid inhaler, and the signs that mean you should see a doctor or dentist.
What is oral thrush and what causes it
Oral thrush, also called oral candidiasis, is a fungal infection of the mouth caused by an overgrowth of Candida, a yeast that lives harmlessly in small amounts in a healthy mouth, gut and on the skin. Under normal circumstances, the balance of bacteria and yeast in the mouth keeps Candida in check. When that balance is disrupted, for example by a change in the immune system, the mouth's natural bacteria, or the local environment, Candida can multiply and cause an infection.
A wide range of factors can tip this balance, including recent antibiotics, which can reduce the "good" bacteria that normally compete with Candida, inhaled or oral steroids, a dry mouth, poorly controlled diabetes, smoking, and anything that weakens the immune system. Oral thrush is not caused by poor hygiene alone, although good oral care does help reduce the risk and speed up recovery once an infection has started.
Recognising the symptoms
The most recognisable sign of oral thrush is creamy white or slightly yellow patches on the tongue, the inside of the cheeks, the gums, or the roof of the mouth. These patches can sometimes be gently wiped away, leaving a red, and occasionally slightly bleeding, area underneath, which is one of the features that helps distinguish thrush from other causes of white patches in the mouth.
Other common symptoms include soreness or a burning feeling in the mouth, a cottony or furry sensation, loss of taste or an unpleasant taste, redness inside the mouth or at the corners of the lips, known as angular cheilitis, and, in more widespread infections, discomfort when swallowing. Symptoms can range from mild and barely noticeable to uncomfortable enough to affect eating and speaking, and they can develop gradually over a few days rather than appearing overnight.
If a white patch does not wipe away, is thickened, or feels like it has always been there, this is less typical of thrush and worth mentioning to a dentist, since a small number of persistent mouth changes need a specific check rather than antifungal treatment.
Who is more likely to get oral thrush
Anyone can develop oral thrush, but some groups are considerably more likely to. Babies and older adults are more susceptible, partly because their immune systems are naturally less robust; in babies it often appears in the first few weeks of life and usually settles quickly with treatment. Denture wearers are also at higher risk, especially if dentures do not fit well, are worn overnight, or are not cleaned thoroughly, since Candida can build up on the denture surface and reinfect the mouth.
People with diabetes, particularly when blood sugar is not well controlled, are more prone to oral thrush, as raised sugar levels in saliva can encourage yeast growth. A weakened immune system, whether from a health condition, chemotherapy, or long-term steroid use, also raises the risk, as does a dry mouth caused by certain medicines or reduced saliva production. Smoking is another recognised risk factor, alongside recent antibiotic use, one of the most common everyday triggers, because antibiotics reduce the normal bacteria that would otherwise help keep Candida under control.
Oral thrush is not usually considered contagious in the way a cold or flu is, since Candida already lives in most people's mouths in small amounts. It can, however, occasionally pass between a breastfeeding parent and baby, causing soreness on the nipples as well as white patches in the baby's mouth, in which case both are usually treated at the same time to stop it passing back and forth.
Treatment options: nystatin, miconazole and fluconazole
Oral thrush is usually treated with a topical antifungal applied directly inside the mouth. Miconazole oral gel and nystatin drops or suspension are typically the first choice, used several times a day for one to two weeks. These are generally well tolerated and act locally on the Candida in the mouth rather than affecting the whole body, and a pharmacist can advise on which option and dose is suitable, including for babies and during pregnancy.
For infections that are more widespread, do not respond to a topical antifungal, or affect the throat as well as the mouth, a GP may consider a short course of fluconazole tablets, which work throughout the body rather than just on the surface. The right choice, dose and length of treatment depends on the severity of the infection and your individual health, so this should always be guided by a pharmacist or clinician who has assessed you, particularly if you take other regular medicines, since some antifungals can interact with them.
Denture wearers also need to treat the denture itself, not just the mouth, by cleaning it thoroughly, removing it overnight, and sometimes soaking it in an antifungal or dilute disinfectant solution recommended by a pharmacist, otherwise the infection can simply return once treatment stops. Keeping dentures out overnight for at least a few hours gives the gum tissue underneath a chance to recover.
Preventing oral thrush, especially with a steroid inhaler
If you use a steroid inhaler for asthma or COPD, you are at higher risk of oral thrush because some of the medicine can settle in the mouth and throat instead of reaching the lungs, where it can locally reduce the mouth's natural defences against Candida. This is a recognised effect of inhaled corticosteroids rather than a sign anything has gone wrong with your asthma treatment, and it does not mean the inhaler needs to be stopped.
Rinsing your mouth with water and spitting it out, rather than swallowing, straight after every dose is one of the simplest and most effective ways to reduce this risk, and using a spacer device with a metered-dose inhaler can also help by reducing how much medicine lands in the mouth rather than reaching the lungs. Cleaning your teeth and, if relevant, your dentures thoroughly and regularly, staying well hydrated to avoid a dry mouth, and keeping any underlying condition such as diabetes well controlled all help lower the chances of oral thrush developing or coming back.
A pharmacist can check your inhaler technique and confirm whether a spacer is suitable for your device, which is often a quick and practical way to cut the risk of recurrent thrush without changing your asthma or COPD treatment itself.
When to see a doctor or dentist
Most cases of oral thrush clear up within one to two weeks with the right antifungal treatment, but some symptoms mean it is worth seeing a doctor, dentist, or pharmacist sooner rather than later. Speak to a healthcare professional if the white patches do not improve after two weeks of treatment, if thrush keeps coming back despite treatment, or if you are not sure whether what you are seeing is actually thrush rather than another cause, such as tonsillitis or a different mouth condition.
Seek prompt medical advice if swallowing becomes painful or difficult, if the infection appears to be spreading down into the throat, or if you have a weakened immune system, since oral thrush can occasionally be a sign of an underlying health issue in these situations. A pharmacist remains a good first point of contact for straightforward oral thrush and can advise on suitable treatment or refer you on if something else needs to be ruled out, including in babies, during pregnancy, or if you are taking other medicines.