Painful small spots on the tongue, cheeks, or palate can significantly affect everyday life. Canker sores, ulcers, and other changes in the oral cavity often appear suddenly and cause discomfort when eating, speaking, or brushing your teeth. Although most of these lesions are not dangerous, it is important to understand what causes them, how to recognise them, and which treatment is most effective.
The most common causes of canker sores and mouth ulcers
A range of factors can lead to painful changes in the oral cavity. Canker sores are among the most common, but it is also important to distinguish them from other types of lesions.
Stress and fatigue – Emotional and physical stress can disrupt immune balance, increasing susceptibility to canker sores.
Mechanical irritation or injury – Cheek biting, aggressive brushing, or irritation caused by orthodontic appliances.
Hormonal changes – In women, canker sores may occur more frequently during menstruation or pregnancy.
Nutrient deficiencies – Low iron, vitamin B12, folic acid, or zinc levels are linked to more frequent canker sores.
Allergies or irritation – Some people react to preservatives, acidic foods, toothpastes containing sodium lauryl sulfate, or certain dental materials.
Systemic diseases – Canker sores may be associated with conditions such as coeliac disease, Behçet’s disease, Crohn’s disease, and HIV infection.
Genetic predisposition – If parents had frequent canker sores, their children are more likely to experience them as well.
How to recognise canker sores
Canker sores (recurrent aphthous ulcers) are small, painful ulcerations that appear inside the mouth—most often on the cheeks, tongue, or the inner surface of the lips. They typically have a white or grey centre with a red border and are not contagious. They may occur as a single lesion or in clusters, and most often heal within 7 to 14 days.
Not every sore in the mouth is a canker sore. It is important to distinguish them from other lesions that require a different approach. Below is a detailed explanation of the most important diagnostic differences.
Diagnostic differences: how to tell canker sores from other lesions
The oral cavity can develop several types of changes that resemble canker sores but have different causes and require different treatment. The most important differences include:
Herpes (Herpes simplex)
Caused by the herpes simplex virus (most commonly type 1).
Usually appears outside the oral cavity, most often on the lip border.
Starts as a cluster of small blisters that later rupture and form a crust.
Contagious and spreads through contact (kissing, sharing cups, utensils).
Often recurs in the same location, with a tingling or burning sensation before the lesion appears.
Leukoplakia
Appears as white patches that cannot be scraped off.
Most commonly results from chronic irritation (e.g., smoking, certain habits).
May be a sign of precancerous change and requires a dental examination.
Typically painless, but persistent and does not resolve on its own.
Candidiasis (oral fungal infection)
Caused by the fungus Candida albicans.
Most commonly occurs in people with weakened immunity, after antibiotics, or with poor oral hygiene.
Visible white deposits can often be gently removed, leaving redness underneath.
May cause burning, dryness, and an unpleasant taste in the mouth.
Traumatic lesions
Occur due to mechanical injury (e.g., biting, sharp tooth or filling edges, hot food/drink).
Ulcers are often larger and have clearly defined borders.
They are not recurrent and heal within a few days once the cause is removed.
They are not primarily related to immune factors.
Recognising these differences is essential for choosing the right treatment and avoiding unnecessary therapies.
Treatment of canker sores and mouth ulcers
In most cases, canker sores heal on their own. However, several approaches can reduce pain, shorten the duration, and support faster recovery.
Topical products (gels, ointments, mouth rinses)
Antiseptics (chlorhexidine) – reduce the risk of secondary infection.
Local anaesthetics (lidocaine gel) – relieve pain and make eating easier.
Anti-inflammatory gels (with hyaluronic acid) – support mucosal healing.
Natural options – for example, propolis, aloe vera, chamomile.
Dietary supplements
Replacing vitamin B12, iron, and zinc may help if canker sores are frequent.
Supplements should be taken only after consulting a doctor.
Maintaining oral hygiene
Brush regularly with a soft toothbrush.
Use toothpaste without sodium lauryl sulfate.
Avoid aggressive mouthwashes that contain alcohol.
Dietary adjustments
Avoid acidic, spicy, and hard foods that may worsen sores.
Drink enough water and choose soft, mild foods while symptoms last.
In more severe cases—when canker sores are very painful, frequent, or prolonged—a dentist or physician may prescribe corticosteroid preparations or recommend further diagnostics.
When should you see a dentist or a doctor?
Although most canker sores and mouth ulcers resolve without medical intervention, certain situations require professional assessment:
If the sores recur more than three times per year
If more than four canker sores appear at the same time
If each individual ulcer is larger than 1 cm and very painful
If the lesions do not heal within 10 to 14 days
If they are accompanied by fever, swollen lymph nodes, or general weakness
If sores occur together with skin or genital changes—this may indicate systemic conditions such as Behçet’s syndrome
In such cases, targeted diagnostics may be necessary, including blood tests, microbiological swabs, and in some instances, a mucosal biopsy.
Prevention: how to reduce the risk of canker sores and ulcers
Canker sores cannot always be prevented, but a few simple habits can reduce the risk:
Maintain gentle and consistent oral hygiene and choose soft-bristled toothbrushes.
Avoid toothpastes containing sodium lauryl sulfate.
Pay attention to diet and reduce irritating foods and beverages.
Increase intake of fresh fruits and vegetables and foods rich in B vitamins, iron, and zinc.
Reduce stress, as chronic stress weakens the immune system.
Avoid trauma: be cautious with sharp foods and chew slowly.
If you wear orthodontic appliances or dentures, check edges regularly and request adjustments if they cause irritation.
For people who experience frequent canker sores, keeping a diary of diet and activities may help identify possible triggers.
Expert advice
If you notice ulcers that keep returning, do not respond to common treatments, or cause significant discomfort, it is best to seek an evaluation by a dentist or dermatologist. Early identification of the cause supports faster healing and helps prevent complications.
At Esthea Polyclinic, we provide professional examinations, personalised therapy, and tailored recommendations for oral mucosal care. Regardless of the cause—mechanical, immune-related, or infectious—our goal is to restore comfort and health to your mouth.