Oral thrush

Overview

Oral thrush is a common fungal infection inside the mouth. It is caused by an overgrowth of yeast (a type of fungus) called Candida. This yeast normally lives in small amounts in your mouth, but sometimes it grows too much and causes white patches, redness, or soreness.

Yes, oral thrush is very common, especially in babies and people who use inhaled steroids for asthma.

Oral thrush can affect people of all ages, but it is most common in infants, older adults, and those with weakened immune systems (such as people with HIV/AIDS or those on chemotherapy). It also affects people who wear dentures, smoke, or have diabetes.

Symptoms

Common symptoms

• White, creamy patches on your tongue, inner cheeks, gums, or tonsils that look like cottage cheese.
• Soreness or redness in the mouth.
• A cotton-like feeling in the mouth.
• Difficulty swallowing or pain when swallowing.
• Loss of taste or an unpleasant taste in the mouth.

Symptoms in children

• White patches in the mouth that cannot be wiped off easily.
• Fussiness or irritability during feeding.
• Diaper rash (because the yeast can also cause thrush on the skin).
• Refusing to feed or eating less than usual.

Symptoms in older adults

• White patches that may be less obvious because the mouth lining can be red and shiny.
• Pain or discomfort when eating or swallowing.
• Cracking at the corners of the mouth (angular cheilitis).
• Difficulty wearing dentures properly.

Causes

Main causes

• Overgrowth of Candida yeast, which normally lives harmlessly in your mouth.
• Taking antibiotics, which can kill the good bacteria that keep Candida in check.
• Using corticosteroid inhalers for asthma or chronic lung conditions without rinsing your mouth afterwards.
• Having a dry mouth (for example, from medications or certain medical conditions like Sjögren's syndrome).

Risk factors

• Being very young (under 1 year old) or older (over 65).
• Having a weakened immune system due to HIV/AIDS, cancer treatment, or organ transplant.
• Having uncontrolled diabetes.
• Smoking or wearing dentures (especially if they do not fit well or are not cleaned properly).
• Taking medications that cause dry mouth or a weakened immune system.

When to see a doctor

See a doctor urgently if:

• If you have difficulty swallowing or pain when swallowing.
• If you have a fever along with mouth symptoms.
• If you have a weakened immune system (due to HIV, chemotherapy, etc.) and develop thrush.

Book a routine appointment if:

• If you notice white patches in your mouth that do not go away after a week of good oral care.
• If you are unsure whether your symptoms are thrush or something else.
• If you have had thrush before and it keeps coming back.

Diagnosis

A doctor or dentist will look at the white patches in your mouth. They will usually be able to tell if it is thrush just by looking. Sometimes they may gently scrape off a small sample of the patch to examine under a microscope or send to a lab for testing.

Tests that may be done

• Visual examination of the mouth.
• Swab of the white patch to check for Candida under a microscope (less common).
• If thrush keeps coming back, your doctor may suggest blood tests to check for underlying conditions like diabetes or immune problems.

What to expect at your appointment

The diagnosis is usually quick and painless. The doctor will look inside your mouth and likely ask about your health history, medications, and any other symptoms. If they take a swab, it may cause a slight discomfort but is not painful.

Treatment

Treatment depends on the severity of the infection and your overall health. For mild cases, simple home care may be enough. For more persistent or severe thrush, your doctor will prescribe medication to kill the yeast. It is important to use the treatment exactly as directed.

Self-care at home

• Practice good oral hygiene: brush your teeth twice a day and floss daily.
• Rinse your mouth after using corticosteroid inhalers.
• If you wear dentures, remove them at night and clean them thoroughly.
• Eat plain yogurt or take probiotic supplements to help restore healthy bacteria (ask your doctor first).
• Avoid mouthwashes that contain alcohol, as they can make dryness worse.

Medical treatments

Your doctor may prescribe an antifungal medicine that you apply directly to the patches in your mouth (like a gel, liquid, or lozenge). For stubborn cases, they may recommend a tablet that you swallow to treat the infection throughout your body. Always complete the full course of treatment, even if your symptoms improve.

Living with this condition

Oral thrush can be uncomfortable, but it usually goes away with treatment. Keep your mouth clean and dry. If you have a chronic condition like diabetes, managing it well can reduce future episodes.

Lifestyle tips

• Quit smoking — smoking makes thrush more likely and harder to treat.
• Reduce sugar intake, as yeast feeds on sugar.
• If you use a corticosteroid inhaler, rinse your mouth with water after each use.

Diet and exercise

A balanced diet helps support your immune system. If thrush makes eating painful, try soft foods like yogurt, soups, or mashed potatoes. Avoid very spicy, salty, or acidic foods that may sting. Regular exercise can help maintain overall health, but it is not directly linked to thrush.

Mental health and emotional wellbeing

Persistent oral thrush can be frustrating and may affect your confidence in social situations. It may cause stress or worry about underlying health problems. If you feel down, talk to your doctor or a counsellor. Remember, thrush is common and treatable.

Prevention

You can lower your risk by keeping your mouth healthy: brush and floss regularly, drink plenty of water, avoid excessive sugar, and if you use an inhaler, rinse your mouth afterward. For breastfeeding mothers, clean feeding equipment properly. For denture wearers, ensure dentures fit well and are cleaned daily.

Complications

If left untreated

• Thrush may spread to the back of the throat, oesophagus (food pipe), or even further into the body, especially in people with weakened immune systems.
• Eating and drinking can become very painful, leading to dehydration or weight loss.
• In very rare cases, the infection can enter the bloodstream and cause a serious condition called candidaemia.

Long-term outlook

With proper treatment, most cases of oral thrush resolve completely within one to two weeks. Even severe cases usually respond well to antifungal medication. If thrush keeps returning, your doctor can help find and manage the underlying cause. The outlook is very good.

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