In the vast majority of cases of oral candidiasis, the culprit is the same: the yeast-like fungus Candida albicans, which normally lives in the mouth of almost every healthy person without causing any symptoms — until something allows it to multiply uncontrollably. This "something" is usually a weakened immune system, weeks without proper oral hygiene, or certain medications that disrupt the microbial balance in the mouth. After diagnosis, the disease is treated with antifungal drugs prescribed by a dentist or physician — gel, tablets, or rinse, depending on the case — combined with enhanced hygiene and almost always a review of the patient's diet or overall health status. At Corona Dental in Barcelona, we explain when white coating in the mouth is indeed candidiasis, and when something else requiring a biopsy lies behind it.
Why does it appear: Candida does not attack, but takes advantage of the moment
Candidiasis cannot be "caught out of nowhere": the fungus is already present, being part of the normal microbiota of most healthy mouths. The infection is triggered by a specific factor that opens the door to uncontrolled growth:
| Risk factor |
Why it promotes infection |
| Broad-spectrum antibiotics |
Destroy bacteria that compete with the fungus for space |
| Poorly controlled diabetes |
Excess glucose in saliva directly feeds the fungus |
| Poorly fitting denture |
Creates a moist, oxygen-free space under the base — ideal conditions for the fungus |
| Inhaled corticosteroids (for asthma) |
The drug settles on the oral mucosa if the mouth is not rinsed after inhalation |
| Xerostomia (dry mouth) |
Saliva normally flushes out the fungus; without it, the fungus accumulates |
| HIV or immunosuppressant use |
The immune system no longer keeps fungal growth in check |
Smoking and a diet high in simple sugars act as additional factors, not independent causes: on their own, they rarely cause candidiasis, but they increase the risk if one of the factors listed above is already present.
Not all candidiasis looks the same: four clinical forms
What many imagine as "thrush" — a white coating that can be scraped off — is only one of four possible forms, and not always the most common one seen in clinical practice.
| Clinical form |
How to recognize it |
| Pseudomembranous |
Curd-like plaques on the tongue or cheeks; easily removed with a gauze swab, leaving a reddened surface underneath |
| Erythematous (atrophic) |
No visible coating, only redness and burning; the form most often missed, typical under a poorly fitting denture |
| Hyperplastic |
White plaques that CANNOT be removed with a swab; most often confused with leukoplakia, requires biopsy if it does not resolve |
| Angular cheilitis |
Red cracks at the corners of the mouth, often in elderly people with pronounced skin folds in this area |
When it is not candidiasis, even though it looks very similar
This is where mistakes are most often made during self-diagnosis via the internet. Leukoplakia also forms white patches in the mouth, but it cannot be scraped off and does not respond to antifungal drugs — therefore, if white patches do not resolve after properly administered treatment, a biopsy ceases to be optional. Oral aphthae, in turn, are painful ulcers with a white-yellow base surrounded by a red halo, but these are isolated lesions that heal on their own within one to two weeks and are not related to Candida fungus. The practical distinguishing criterion: pseudomembranous candidiasis is scraped off with a gauze swab (with redness underneath); leukoplakia is not.
Diagnosis and when to see a doctor
In most cases, a clinical examination is sufficient for diagnosis — the appearance of the coating and whether it can be scraped off with a spatula. If the form is hyperplastic, if there is no improvement after a full course of treatment, or if there is any doubt about a suspicious lesion, cytological scraping, culture on Sabouraud medium, or biopsy is performed. A doctor should be consulted without delay if, in addition to the coating, there is difficulty swallowing (possible spread to the esophagus), fever, or if the patient already has a weakened immune system — in these cases, the infection may not be limited to the oral cavity.
Treatment: topical first, systemic if necessary
The approach depends on the extent of the lesion and whether there are uncontrolled underlying factors. In mild and localized cases, topical treatment is usually sufficient; in moderate, widespread cases, or when there is no response to topical therapy, the physician considers switching to systemic treatment.
| Topical treatment |
Systemic treatment |
| Nystatin suspension, applied topically several times a day |
Fluconazole orally, as a short course, prescribed by a dentist or physician |
| Miconazole oral gel, applied to the affected area |
Used in widespread cases or when there is no response to topical treatment |
| First-line therapy for mild, localized cases |
Requires evaluation of interactions with other medications |
| Improvement within 2–3 days |
Typical course: 7 to 14 days under medical supervision |
An important detail that is rarely mentioned: miconazole can interact with other medications — including certain anticoagulants — so it is always necessary to inform the physician of all medications being taken before starting treatment. And no matter how quickly symptoms improve within two to three days, treatment should be continued for another 48 hours after symptoms disappear: stopping early as soon as discomfort subsides is the most common cause of immediate recurrence.
If treatment does not help
If there is no improvement after a complete and properly administered course, two possibilities should be considered before repeating the same drug: either it is a different species of Candida with natural resistance to the most common antifungals — which can only be confirmed by culture — or it is not candidiasis at all, and the next logical step is a biopsy. Repeating the same treatment without additional diagnostics is the most common mistake in cases that do not resolve on the first attempt.
Denture hygiene: the most recurring cause
In elderly people with removable dentures, candidiasis under the denture — the erythematous form, without visible coating — is by far the most common reason for consultation. The denture should be cleaned outside the mouth every evening with a brush and neutral soap, never with abrasive toothpaste, and immersed in an antiseptic solution — baking soda solution or chlorhexidine — for 10–15 minutes before bedtime. Sleeping with the denture in the mouth, without this nightly rest for the mucosa, is probably the most common habit that perpetuates this particular type of candidiasis, even more than insufficient hygiene during the day.
Prevention and why candidiasis recurs so often
Oral candidiasis recurs in a significant proportion of patients if the underlying factor that caused it is not addressed — treating the infection without correcting a poorly fitting denture or without improving diabetes control usually results in recurrence within a few months. Rinsing the mouth with water after using a corticosteroid inhaler significantly reduces the risk of this particular type of candidiasis. Moderate sugar intake, good oral and denture hygiene, and smoking cessation complement the most effective prevention according to available data.
Frequently asked questions about oral candidiasis
Is oral candidiasis contagious?
In healthy adults, it does not behave like a typical contagious infection, since Candida is already present in the mouths of most people. Transmission through close contact is nevertheless possible, and this is especially relevant for newborns, who can acquire the fungus during passage through the birth canal or through contact with contaminated surfaces, such as a poorly sterilized pacifier.
How long does treatment for oral candidiasis take?
With proper treatment, symptoms improve within 2–3 days, and a full course usually lasts 7 to 14 days depending on the extent and response to therapy. It is critically important to continue treatment for another 48 hours after symptoms disappear, even if it seems unnecessary: stopping early is the most common reason for the infection to return almost immediately.
Can candidiasis occur without white coating?
Yes, and it is more common than it seems. The erythematous form occurs without visible coating — only redness and burning, especially under a denture. Many people live with this form for months without a diagnosis because it does not match the typical image of "oral fungus."
Does oral candidiasis always indicate a serious illness?
Not necessarily. In infants and in people who have recently taken antibiotics, it often occurs without any underlying disease. It is indeed more common and more difficult to treat in people with poorly controlled diabetes or HIV — in these cases, it is worth checking how well the underlying condition is being managed, rather than focusing only on treating the oral cavity.
Can oral candidiasis be prevented with probiotics or yogurt?
This may help as part of a broader strategy, especially after a course of antibiotics, but it does not replace antifungal treatment once the infection has developed. Their role is rather preventive — helping to restore the balance of the oral microbiota — rather than therapeutic for already diagnosed candidiasis.
Oral candidiasis in Barcelona, Eixample district
Corona Dental is located at c/Entença, 69, Barcelona, a two-minute walk from Rocafort metro station (line L1). Diagnosis and follow-up for oral candidiasis, as well as assessment of poorly fitting dentures that may contribute to it, are performed in a single clinic. The clinic has been operating since 2009 in the Eixample district. Health registration number: E08706004.
