Oral Thrush (Oral Yeast Infection)

What causes oral thrush

Candida yeast normally lives in the mouth in small amounts without causing problems. Thrush develops when the balance of microbes or the body's defenses change, allowing yeast to multiply.

Risk factors include:

• age: newborns and babies (immature immune systems), and older adults
• dentures, especially if worn overnight or poorly fitting
• antibiotics, which kill helpful bacteria
• inhaled corticosteroids for asthma or COPD, especially without rinsing the mouth afterward, and oral steroids
• dry mouth from medicines, Sjögren's syndrome, or radiation to the head and neck
• diabetes, especially poorly controlled
• weakened immune system: HIV, chemotherapy, organ transplant medicines
• smoking
• iron, folate or B12 deficiency

Symptoms

In adults

• creamy white or yellowish patches on the tongue, inner cheeks, gums, palate or throat
• patches can be wiped off, leaving red, sometimes bleeding areas
• soreness or burning, especially when eating
• a cottony feeling in the mouth
• loss or change of taste
• cracking and redness at the corners of the mouth (angular cheilitis)
• redness and soreness under dentures (denture stomatitis)

Some forms show red, raw areas rather than white patches (erythematous candidiasis), particularly after antibiotics or under dentures.

In babies

• white patches on the tongue, gums and inner cheeks that look like milk curds but do not rub off easily
• fussiness or reluctance to feed
• a related yeast diaper rash: bright red with small red spots at the edges
• the breastfeeding parent may get nipple thrush: burning or shooting pain, shiny pink nipples

Milk residue on the tongue is common and wipes off easily, unlike thrush.

Oral thrush vs other white patches

Diagnosis

Thrush is usually diagnosed by its appearance. A doctor may take a scraping or swab to confirm yeast under the microscope or with a culture, especially if it is recurrent or not responding. If thrush has no obvious cause, blood tests for diabetes, blood count and sometimes HIV may be suggested. An endoscopy is done if esophageal candidiasis is suspected.

Treatment

Babies

• nystatin oral suspension applied inside the mouth several times a day, or miconazole oral gel (not recommended for babies under 4 months in some countries because of choking risk; follow your pediatrician's advice)
• treat the breastfeeding parent's nipples at the same time if they have symptoms
• sterilize bottle nipples and pacifiers daily

Adults

• mild cases: clotrimazole lozenges, miconazole buccal tablets or nystatin suspension, typically for 7 to 14 days
• moderate to severe cases or immunocompromised people: oral fluconazole tablets
• denture care: remove dentures at night, clean them daily, soak in an antifungal or denture-cleaning solution, and treat the mouth at the same time

Addressing the cause

• rinse your mouth with water and spit after using a steroid inhaler, and use a spacer
• improve blood sugar control
• treat dry mouth
• stop smoking

Prevention

• rinse after inhaled steroids
• brush teeth twice daily and clean dentures properly; take them out overnight
• attend regular dental checkups
• manage diabetes well
• avoid unnecessary antibiotics

Frequently asked questions

What causes oral thrush?

Oral thrush is caused by an overgrowth of Candida yeast. Common triggers include antibiotics, steroid inhalers, dentures, dry mouth, diabetes, smoking and a weakened immune system. In babies, it is common because their immune systems are still developing.

What does oral thrush look like?

It usually appears as creamy white patches on the tongue, inner cheeks or palate that can be wiped off, leaving red, sore areas. It may also cause cracked corners of the mouth or redness under dentures.

How do you get rid of oral thrush?

Antifungal treatments such as nystatin suspension, miconazole gel, clotrimazole lozenges or fluconazole tablets clear most cases within 1 to 2 weeks. Addressing the cause, such as rinsing after inhaler use or cleaning dentures, prevents it coming back.

Is oral thrush contagious?

Candida is present in most people, so thrush is not considered very contagious in healthy adults. It can pass between a breastfeeding baby and parent, which is why both are often treated together.