Oral Thrush: Why Do Some People Keep Getting It?

Oral thrush is usually easy to treat. The difficulty for some people is that it comes back, sometimes within weeks of finishing treatment. When that happens, the important question is no longer how to clear the infection but why the mouth keeps allowing it to return. Recurrent thrush is nearly always a signal pointing at something else, and identifying that something is the key to breaking the cycle.

What Is Oral Thrush?

Oral thrush, or oral candidosis, is an overgrowth of Candida, a yeast that lives harmlessly in most people’s mouths. Problems occur only when the balance shifts and the yeast multiplies beyond what the mouth’s normal defences keep in check.

The organism itself is not usually the issue. The change in conditions that allowed it to flourish is.

What Does It Look and Feel Like?

Thrush takes several forms. The best known is the pseudomembranous type, with creamy white patches on the tongue, palate or inner cheeks that can be wiped away to leave a red, sometimes bleeding surface underneath.

Other presentations are easier to miss. Erythematous candidosis appears as flat red areas, often on the palate or the top of the tongue, and can cause soreness or burning without any white patches at all. Angular cheilitis produces cracked, sore corners of the mouth. Denture associated inflammation shows as redness confined to the area covered by an upper denture.

Symptoms range from nothing at all to burning, soreness, a cottony feeling, altered taste or discomfort when eating.

Why Do Some People Keep Getting It?

Recurrence usually comes down to one or more persistent local or systemic factors.

Inhaled corticosteroids (puffer) for asthma or COPD are among the most common causes, particularly when the mouth is not rinsed after each dose. Dry mouth, whether from medications, medical conditions or previous radiotherapy, removes the flushing and antimicrobial action of saliva that normally keeps Candida in check. Dentures create a warm, sheltered surface for the organism to colonise, especially when worn overnight or not cleaned thoroughly.

Systemic factors also matter. Poorly controlled diabetes, iron, vitamin B12 or folate deficiency, thyroid disease, immunosuppressive medication and any condition affecting immune function all increase susceptibility. Recent or repeated courses of broad spectrum antibiotics disturb the normal balance of oral organisms. Smoking is an independent risk factor.

In a smaller number of cases, recurrent thrush is the first sign of an undiagnosed underlying condition, which is one reason persistent cases warrant proper assessment.

Why Is Treating the Infection Alone Often Not Enough?

Antifungal treatment reduces the yeast load, so symptoms improve. If the conditions that allowed the overgrowth remain unchanged, the population simply rebuilds once treatment stops.

This is why repeated courses of antifungal medication without investigation tend to produce a cycle of clearing and returning. Repeated exposure can also select for organisms that respond less well to standard treatment. The more useful approach is to treat the current episode while working out what is driving the recurrence.

How Is Recurrent Thrush Investigated?

Assessment starts with a detailed history covering your medications, particularly inhalers and antibiotics, your medical conditions, denture habits, smoking and any symptoms of dry mouth.

Examination looks at the pattern and distribution of the changes, the condition and fit of any dentures, and the state of the mouth generally. A swab or scraping sample may be taken to confirm the organism and, where relevant, test which antifungals it responds to. Blood tests are frequently arranged to check for iron levels, vitamin B12, folate, blood glucose or HbA1c, full blood count and sometimes thyroid function. If an area does not respond to treatment as expected, a biopsy may be recommended, since some other conditions can look similar.

What Can I Do to Reduce the Chance of It Returning?

Rinse your mouth with water and spit out after every dose of an inhaled corticosteroid, and use a spacer if one has been prescribed. If you wear dentures, remove them overnight, clean them thoroughly each day, and store them dry or as directed rather than in a warm moist environment.

Keep up careful oral hygiene, including cleaning the tongue gently. Address dry mouth with regular sips of water, sugar free chewing gum and any saliva substitutes recommended for you. If you smoke, stopping reduces the risk. Where diabetes is present, working with your GP to control your blood sugar levels is an important part of prevention rather than an unrelated issue.

When Should I Have It Checked?

See a clinician if thrush returns after treatment, if it does not clear with a standard course, if you have white or red patches that persist, or if your mouth is regularly sore or burning. Any white or red area that does not resolve after appropriate treatment should be reassessed rather than treated repeatedly, because other conditions can present in a similar way and are better identified early.

To learn more, call us on (08) 9376 6789.

IMPORTANT: This content is for general information purposes only. It does not constitute medical or dental advice. Readers should consult a qualified health professional regarding any personal health concerns.