The difference between oral thrush and other conditions affecting the oral mucosa

Oral thrush is one of the most common oral fungal infections and occurs when the balance of the microbial flora is disrupted. Usually, the causative agent is Candida albicans, a fungus normally present in the oral cavity but which, under favourable conditions, can multiply excessively and cause inflammation and discomfort.

This condition is often confused with other problems affecting the oral mucosa, such as mouth ulcers, cold sores or lichen planus, which is why correctly recognising the symptoms and consulting a doctor are essential. In this article, we will explain what oral thrush is, how it differs from other conditions, and what treatments are recommended.

Oral thrush, also known as oral candidiasis, is an infection caused by the uncontrolled growth of the fungus Candida albicans. It can occur at any age and affects both adults and children.

Candida albicans and oral infection

Candida albicans normally lives in the mouth, but when immunity is low or certain contributing factors are present (antibiotic treatment, poorly-fitting dentures, diabetes, smoking), it can transform from a harmless organism into a pathogen.

Symptoms of oral thrush

Oral thrush usually begins suddenly and is characterised by the appearance of whitish, ‘curd-like’ deposits on red, inflamed mucous membranes. These deposits can be wiped away and frequently appear on the tongue, the inside of the cheeks, the roof of the mouth or in the oropharynx, and less commonly on the gums.

In addition to these visible lesions, patients may also experience other symptoms, such as:

• a burning or stinging sensation in the mouth
• discomfort when chewing and speaking
• minor bleeding when the whitish deposits are removed
• cracks and redness at the corners of the mouth (angular cheilitis)
• altered taste, sometimes metallic

A specific form of candidiasis is denture stomatitis, which occurs in patients wearing acrylic dentures, particularly upper dentures. This is exacerbated by factors such as poor denture fit, food retention and poor oral hygiene. In such cases, regular check-ups with the dentist are essential for adjusting the dentures and preventing infections with Candida albicans.

It is important to note that the symptoms of oral candidiasis can easily be confused with other oral conditions (canker sores, lichen planus, herpes), which is why the diagnosis must be made exclusively by a dentist, based on a clinical examination and, if necessary, further investigations. 

High-risk patient groups

• people with a weakened immune system (patients with HIV, cancer, diabetes, autoimmune diseases)
• the elderly and infants
• pregnant women
• patients who wear dentures or have poor oral hygiene
• people undergoing long-term treatment with antibiotics, corticosteroids or chemotherapy

At present, the incidence of oral thrush is on the rise due to the increasing number of cases of immunodeficiency (HIV, autoimmune diseases), the development of resistance to antifungals, and the growing proportion of older people in the general population. Although there is no preference for a particular sex, Candida albicans is more commonly detected in women’s saliva.

“Cases of oral candidiasis are quite common, regardless of the patients’ age. I had a patient who was a smoker and had poor oral hygiene; she came to the surgery with whitish deposits on her tongue and a change in taste, even after she had been rinsing with bicarbonate of soda for several days. Following a clinical examination, I explained to her that she had a form of oral thrush requiring medication. I carried out a professional cleaning, discussed with the patient how to improve her brushing technique and the use of aids such as dental floss or a mouthwash, and emphasised the importance of regular check-ups with the dentist to detect any problems at an early stage. Together, we drew up a personalised treatment plan for the candidiasis, which involved taking an antifungal medication and using a chlorhexidine mouthwash to reduce the inflammation.” – Dr Irina Popa, dentist at the DENT ESTET clinics. 
 

Although many patients confuse mouth ulcers with oral thrush, the two conditions are different, both in terms of appearance and in terms of their progression and treatment.

What do mouth ulcers look like compared to oral thrush?

Canker sores are small, round-to-oval ulcers with red edges and a whitish or yellowish centre. They usually appear on the inside of the cheeks, on the tongue or on the lips and are accompanied by a burning sensation a few hours before they become visible. They are very painful and cause discomfort when chewing and speaking. They generally heal within 7 to 14 days without leaving scars, but may recur periodically.

Unlike mouth ulcers, oral thrush manifests as whitish deposits resembling curdled milk, which can be wiped away, leaving a red, sensitive and sometimes bleeding mucous membrane. Lesions frequently appear on the tongue, cheeks, roof of the mouth and oropharynx. In addition, patients may experience a burning sensation, a metallic taste or cracks at the corners of the mouth.

Duration and progression of the two conditions

• Canker sores clear up on their own within 1–2 weeks, but they tend to recur periodically, particularly in people who are stressed, tired or have nutritional deficiencies.
• Oral thrush, on the other hand, does not clear up on its own and requires antifungal treatment. If left untreated, the infection can progress and even spread throughout the body. 
   

Although, in the early stages, oral herpes and oral thrush can be confused, the two conditions have completely different causes, symptoms and treatments.

Oral herpes is caused by the herpes simplex virus type 1 (HSV-1), which is transmitted through direct contact with the saliva or secretions of an infected person. Once it has entered the body, the virus remains dormant and can recur throughout a person’s life, particularly during periods of stress or when the immune system is weakened.

Herpes manifests as small clusters of blisters, which burst and leave behind painful, superficial ulcers with red edges. Common sites include the gums, the roof of the mouth, the lips and, occasionally, the interdental papillae. Unlike oral thrush, where the whitish patches may be wiped away, herpetic lesions are more obvious and do not come off.

A key difference between herpes and oral thrush is contagiousness:

• Herpes is highly contagious and spreads rapidly through direct contact.
• Oral thrush can also be transmitted, but much less readily, usually via saliva or contaminated cutlery.

Duration and recurrence

• Herpes lasts, on average, 7–12 days, but can recur several times a year.
• Oral thrush, if left untreated with antifungal medication, does not clear up on its own and may worsen. In severe cases, patients often search for information such as ‘rapid treatment for oral thrush’ or ‘bicarbonate of soda for oral thrush’, but the only correct solution remains a visit to the dentist. 
   

Lichen planus and oral thrush can be confused by patients, as both cause visible changes to the oral mucosa. However, their causes and treatments are completely different.

Lichen planus is a chronic inflammatory condition of an autoimmune nature, in which the immune system attacks the body’s own cells in the oral mucosa. It is more common in women over the age of 50 and may be associated with severe stress or other chronic conditions, such as diabetes or lupus.

What does lichen planus look like?

Lesions caused by lichen planus can take several forms:

• keratotic – whitish lines or patches, resembling a network
• atrophic or ulcerative – red, painful areas
• bullous – with blisters that may burst

These are usually symmetrical and appear on the inside of the cheeks, on the tongue, gums or lips. In contrast, oral thrush manifests as whitish patches that can be wiped away, leaving the mucous membrane red and sensitive.

Lichen planus can be exacerbated by stress, local trauma or poor oral hygiene. Sometimes, the lesions may become super-infected with Candida albicans, which complicates the diagnosis.

Unlike oral thrush, where the diagnosis is clinical and antifungal treatment takes effect rapidly, lichen planus often requires a biopsy for confirmation and to rule out the risk of malignant transformation. 

Sometimes, lesions in the mouth are not caused by oral thrush, but by other general conditions, particularly digestive or metabolic ones. These may have similar symptoms and must be correctly distinguished by a doctor.

Diabetes 

Patients with diabetes are more prone to oral problems such as dry mouth, periodontal infections and even recurrent oral thrush. Chronic hyperglycaemia reduces the body’s ability to fight off infections, and the oral mucosa becomes more vulnerable.

Coated tongue (‘thick tongue’)

Coated tongue occurs when bacteria, dead cells and food debris accumulate on the surface of the tongue, forming a whitish or yellowish coating. Although it resembles thrush on the tongue, it is not the same thing. Generally, coated tongue clears up with proper oral hygiene, but it can sometimes be a sign of digestive or respiratory problems.

Gastro-oesophageal reflux

Patients with acid reflux may experience heartburn, halitosis and tooth erosion, as well as inflammation of the oral mucosa. These lesions can be mistaken for those caused by oral thrush, which is why a differential diagnosis is essential.

Any persistent change in the appearance of the oral mucosa – whitish patches, a burning sensation, or ulcers that do not heal – should be assessed by a dentist. Only a specialist can determine whether it is oral thrush or another condition, some of which may be linked to serious systemic illnesses.

Oral thrush is a common infection, but it is often confused with other conditions affecting the oral mucosa, such as mouth ulcers, cold sores or lichen planus. The differences in appearance, causes and progression are essential for establishing a correct diagnosis and effective treatment.

Although remedies such as salt water or bicarbonate of soda may relieve symptoms, they are no substitute for the antifungal treatment recommended by a doctor. It is important that patients do not ignore the symptoms and attend regular dental check-ups. In this way, complications can be prevented, and treatment can be swift and effective.