Canker sores are one of the most common oral health problems. Have you ever had one and didn’t know why? Here’s everything you need to know about their causes and treatment.
What is a mouth ulcer or canker sore?
Canker sores, also known as mouth ulcers, are superficial lesions that appear on the soft tissues of the oral cavity: lips, cheeks, tongue, and gums. They can cause discomfort when speaking or eating. Although in most cases they are mild and disappear on their own, it is important to know their cause in order to treat them correctly.
What types of sores can we find?
We can distinguish three types of oral ulcers depending on their size and duration:
Minor canker sores
Minor canker sores are the most common. They measure less than one centimeter, usually heal spontaneously in one or two weeks, and do not leave a scar.
Major canker sores
Larger canker sores are deeper and more painful. They can exceed one centimeter in diameter and take several weeks to heal. In some cases, they can leave a scar.
Herpetiform ulcers
Multiple small lesions appear in clusters and may merge together. Despite the name, they are not always related to the herpes virus.
Symptoms of sores
Although the appearance of the wound is the most obvious sign, the development of a canker sore usually follows a very characteristic process accompanied by the following symptoms:
Prodromal phase
Between 24 and 48 hours before the sore becomes visible, it is common to feel a tingling, itching, burning, or stinging sensation in the exact area of the mucosa where it will erupt.
The appearance of the canker
Once it appears, a canker sore presents as a round or oval ulcer. Its center is white, grayish, or yellowish (due to fibrin, a protein that aids in healing), surrounded by a bright red border or halo due to inflammation.
Local pain and tenderness
The pain is sharp and intensifies noticeably with mouth movement when speaking, brushing teeth, or coming into direct contact with crunchy, acidic, salty, or highly spiced foods.
General symptoms in more severe cases
When the sores are very large or appear in multiple outbreaks, the patient may experience a general feeling of malaise that includes fever, tiredness, or even swelling of the lymph nodes located under the jaw or in the neck.
Why do mouth sores appear?
The causes of mouth ulcers are very varied. They can range from a simple blow to a systemic disease. We can distinguish the following canker sores depending on their origin:
Traumatic ulcers
These are those caused directly by a mechanical or physical impact on the oral mucosa. The most common causes include:
- Accidental bites while chewing.
- Chafing and irritation caused by braces or other orthodontic appliances.
- Poorly fitting or ill-fitting dentures.
- The continuous rubbing against the sharp edge of a broken tooth or a worn-out filling.
- Burns from ingesting excessively hot or acidic food or liquids.
Recurrent aphthous stomatitis (RAS)
This is the most common form of recurrent canker sores. Although it is especially frequent in children and young adults, it can persist throughout a person’s adult life, often linked to periods of stress or fatigue. Its exact cause remains unknown, so it is considered a multifactorial condition. These are the main contributing factors:
Genetic factors
Genetics can predispose individuals to developing these types of sores. If one or both parents suffer from frequent mouth ulcers, the likelihood of their children developing them increases significantly due to a familial sensitivity in the inflammatory response of the oral mucosa.
Alterations in the immune system
The immune system has a very direct relationship with the development of canker sores. During times of physical or emotional stress, weakened immune system, or extreme fatigue, the immune system can experience a temporary imbalance and trigger an exaggerated inflammatory response in the oral mucosa.
Nutritional deficits
A deficiency in certain essential nutrients weakens tissue structure and the immune system, potentially contributing to the development of mouth ulcers. These include deficiencies in iron, folic acid, and B vitamins (especially B1, B2, B6, and B12), as well as vitamins C, A, and E.
Hormonal changes
Fluctuations in estrogen and progesterone levels directly influence the permeability of mucous membranes. Therefore, many women experience outbreaks of canker sores coinciding with specific phases of their menstrual cycle or during pregnancy.
Stress and anxiety
As with so many other things, stress and anxiety are two terrible allies when it comes to managing canker sores. Emotional stress and lack of sleep are clearly linked to outbreaks in many patients.
Quit smoking
Quitting smoking can also cause mouth ulcers during the first few weeks. This is because cigarette smoke causes an increase in the thickness of the keratin layer lining the mouth (hyperkeratosis), which acts as an artificial “shield.” When you quit, the mucous membrane returns to its normal thickness and becomes temporarily more sensitive. However, it’s important to remember that overall health benefits of quitting smoking always far outweigh such a minor problem as mouth ulcers.
Aphthous ulceration secondary to chemotherapy or radiotherapy
This is a common side effect in patients undergoing cancer treatment. Certain chemotherapy drugs, such as methotrexate, 5-fluorouracil, and doxorubicin, impair the regenerative capacity of mucous membranes and can contribute to the development of these types of lesions in the mouth. Radiation therapy to the head and neck can also cause mucositis, a severe inflammation of the inside of the mouth characterized by painful ulcers on the gums and tongue.
Sores caused by systemic diseases
Oral and general health are closely linked as we’ve discussed in other articles. Therefore, certain systemic diseases such as celiac disease, ulcerative colitis, Behçet’s syndrome, or Crohn’s disease can cause mouth ulcers.
Sores caused by infectious diseases
The herpes simplex virus (HSV-1) causes herpetiform ulcers, a cluster of small blisters that, when they rupture, leave sores on the lips or oral mucosa. Herpetic lesions are highly contagious unlike common sores.
How to cure canker sores
We’ve already seen that there are different types of canker sores, and not all of them heal in the same way. Generally, smaller canker sores are benign and usually disappear on their own within 10 to 14 days without leaving any scars. Larger or herpetic-type canker sores can last up to a month and sometimes leave small scars. Although the body usually resolves the problem on its own, we can intervene to reduce pain and speed up healing.
Symptomatic treatment for sores
Since most canker sores do not have a single curable cause, the dentist’s primary focus is on relieving discomfort through:
Protective gels
These types of gels usually contain hyaluronic acid or bioadhesives that form a film over the sore, isolating it from friction, saliva, and food acids.
Rinses with coconut oil
Coconut oil contains lauric acid, a medium-chain fatty acid that can be converted into monolaurin, compounds that have been attributed with antimicrobial and anti-inflammatory effects. Therefore, used as a mouthwash may help reduce bacterial load, soothe irritation, and create a more favorable environment for sore healing.
Topical anesthetics
Topical anesthetics are ideal for applying occasionally before meals in cases where the pain from the sore may difficult proper eating.
Topical or systemic corticosteroids
The dentist may prescribe the use of corticosteroids in gels, compounded formulas, or, exceptionally, orally to stop the inflammatory outbreak in particularly severe, painful, or recurring cases.
Rinses with chlorhexidine
This antiseptic helps keep the area free of bacteria, preventing the sore from becoming infected and taking longer to heal.
Home remedies for mouth sores
It is advisable to follow these guidelines on a daily basis to ensure a quick recovery and avoid complications:
Maintain rigorous oral hygiene
Brush your teeth gently after each meal using a soft-bristled toothbrush to avoid further irritating the area. Maintaining good oral hygiene will prevent the ulcer from becoming infected.
Take care of your diet
Temporarily avoid very spicy, salty, acidic foods (such as citrus fruits or tomatoes) or foods with excessively crunchy and hard textures that may scratch the ulcer.
Avoid chemical irritants
Do not use mouthwashes or toothpastes that contain alcohol or sodium lauryl sulfate, as they can dry out the area and worsen the condition of the lesion.
Consult a specialist
If you have persistent mouth sores, it’s essential to have a full blood test to check for any undiagnosed vitamin deficiencies, food allergies, or systemic conditions. Similarly, if you have any mouth ulcers that don’t heal or last for more than three weeks, they should be evaluated immediately by a healthcare professional to rule out more serious conditions.
How to prevent the development of mouth ulcers
If you don’t currently have mouth ulcers, but want to prevent them from developing, here are some tips for prevention:
Take care of your oral health
Maintaining good oral hygiene, visiting the dentist regularly, and correcting prostheses or appliances that may cause chafing can help you avoid this problem.
Pay attention to what you eat
Eating a balanced diet that avoids vitamin deficiencies can be a good way to combat canker sores. Similarly, avoiding very hard, very hot, and/or very spicy foods can also help.
Monitor your stress
We know it’s not always easy, but we also want to encourage you to try to lead a calmer, less stressful life with time to sleep properly, which is essential for maintaining good oral and general health.
Diseases that look like canker sores… but aren’t
Not every mouth sore is a canker sore. Most common canker sores are painful, have a whitish or yellowish center, a red border, and usually heal on their own within 1 to 2 weeks. But there is an important warning sign: any lesion, ulcer, lump, or white or red spot that doesn’t heal within 3 to 4 weeks should be checked by a professional. Often, it’s due to benign causes, as we’ve seen, but if the lesion persists, grows, bleeds, hardens, or changes in appearance, a biopsy may be necessary to rule out a potentially malignant lesion. Among the lesions that can be mistaken for canker sores are:
Leucoplasias
White patches that do not come off when scraped. Although mostly benign, they are considered premalignant lesions that require close clinical monitoring to ensure they do not progress negatively.
Erythroplasias
Persistent red spots with a velvety appearance. They have a significantly higher risk of becoming malignant than white spots, so early diagnosis is a top priority.
Oral lichen planus
A chronic inflammatory disease of immune origin. It manifests as intertwined white lines, erosive areas, or very bothersome sores that usually appear symmetrically on both sides of the cheeks.
Specific infections of the mouth
Fungal infections such as oral candidiasis or bacterial infections such as syphilis in its early stages. These conditions can present with ulcerated lesions very similar to a common canker sore, but require specific antimicrobial treatment.
Chronic traumatic ulcers
Injuries caused by continuous friction over time, such as from an exposed tooth root or a broken prosthesis. If the stimulus is not eliminated, the ulcer will not heal and the tissue may suffer serious alterations.
Oral cancer
The most common type is oral squamous cell carcinoma. It usually appears as a painless ulcer in its initial stages, but it hardens over time. It is commonly detected in critical areas such as the sides of the tongue, the floor of the mouth, the gums, the buccal mucosa, the palate, or the lips. More information about oral cancer.
Therefore, keep this idea in mind: a sore that appears and disappears is usually a canker sore; a lesion that remains, changes, or does not heal should be checked.
