Canker sores - Causes, Symptoms, and Treatments
Canker sores - Causes, Symptoms, and Treatments

Canker sores are small superficial ulcers that form, most often, on the mucous membranes inside the mouth: on the inside of the cheeks, tongue, inner side of the lips, palate, or gums.

Canker sores can also appear on the genitals, but rarely. This will only be about canker sores in the mouth.

When canker sores occur repetitively, it is called aphthosis. The word stomatitis means inflammation of the mucous membranes from inside the mouth.

Mouth ulcers are common: about 17% of the population is affected at some point in their lives. Often, the first outbreak of canker sores appears during childhood. Then, the symptoms return at certain periods and then disappear permanently during the thirties.

Canker sores: how to recognize them?

There are 3 forms of mouth ulcers:

Minor form

From 1 to 5 oval-shaped ulcers (2 mm to 1 cm in diameter) that heal naturally in 7 to 14 days without leaving a scar. Canker sores occur in this form in 80% of cases.

Major or annoying form

Larger ulcers (more than 1 cm in diameter), with an irregular contour, which can take 6 weeks to heal and often leave scars

Herpetiform or miliary form

From 10 to 100 tiny ulcers (less than 3 mm in diameter) with irregular contours that gradually gather and then form an ulcerative area, which persists for 1 to 2 weeks without leaving a scar.

Evolution of canker sores

The pains last most of the time from 2 to 5 days.

However, ulcers may need 1 to 3 weeks to heal.

Diagnosis of aphthous stomatitis

The canker sore is a round or oval wound, painful, and occurs in flare-ups.

To make the diagnosis of canker sore, the doctor relies on several characteristics:

  • the background yellowish (“fresh butter”) or greyish;
  • the infiltrated base (you can take the canker sore between your fingers and you feel that the whole area is discreetly indurated);
  • The edges are sharp and surrounded by a bright red halo.

When mouth ulcer-like symptoms occur recurrently, it is best to consult a doctor. The latter will carry out a complete medical examination, which will allow him to make a diagnosis.

If, in addition to canker sores, redness in the eyes, joint pain, persistent diarrhea or abdominal pain are present, it is important to consult without delay.

Chronic disease can also cause ulcers similar to canker sores, such as inflammatory bowel disease (Crohn’s disease or ulcerative colitis), celiac disease, or Behçet’s disease.

In addition, canker sores can look like mucositis: an inflammation of the lining of the mouth that sometimes creates small lesions. Individuals with weakened immune systems (due to HIV infection or cancer treatment, for example) are more likely to have ulcers that could be mistaken for canker sores.

Causes of mouth ulcers

The causes of aphthous stomatitis are not yet well established.

Canker sores are not of infectious origin, therefore not contagious. Several factors, including heredity, could contribute.

However, scientists have noted factors that tend to trigger symptoms in sufferers:

A small wound inside the mouth

It can be caused by a bad fit of dental prosthesis, oral surgery, too energetic use of the toothbrush, chewing of the cheek, etc …

Physical fatigue and stress

They often precede the appearance of canker sores.

Food allergies or sensitivities

The recurrence of canker sores is reported in the scientific literature to be associated with food allergies or sensitivities (for example, to coffee, chocolate, eggs, nuts, cheese, highly acidic foods, and preservatives, such as benzoic acid and cinnamaldehyde 1-4).

A dietary deficiency

In vitamin B12, zinc, folic acid, or iron.

Smoking cessation

Canker sores can occur during smoking cessation.

An infection with the bacterium Helicobacter pylori

This is the same bacteria that can cause an ulcer in the stomach or small intestine.

Taking certain medications

Certain medications, such as nonsteroidal anti-inflammatory drugs (ibuprofen and others), beta-blockers (propranolol and others), and alendronate (for osteoporosis).

Hormonal changes

They may be related to the menstrual cycle, possibly. Canker sores tend to appear during menstruation, but this link is uncertain.

Note: Using toothpaste containing sodium dodecyl sulfate (called sodium lauryl sulfate), an ingredient in most toothpaste, may increase the risk of developing canker sores. It would make the inside of the mouth more vulnerable to injury by removing the protective layer that lines it.
However, this hypothesis remains to be verified. A few small clinical trials suggest that the use of toothpaste without sodium dodecyl sulfate reduces the frequency of canker sore periods. However, a more recent clinical trial concluded that the type of toothpaste used had no influence on canker sores.

Do you regularly have mouth ulcers?

Discover the detailed symptoms of these small ulcers and how to reduce their frequency of occurrence with simple tips to apply on a daily basis.

What are the symptoms of mouth ulcers?

The outbreak of canker sores can be identified thanks to 3 symptoms.

First of all, it is often preceded by a tingling sensation in the affected area.

Then one or more small ulcers appear inside the mouth. The center of the ulcers is whitish, and their outline is red.

Finally, canker sores are recognizable because they cause severe pain, comparable to a burning sensation. Moreover, the word canker sore comes from the Greek “aptein” which means “to burn”.

The pain is accentuated when talking or eating, especially during the first few days.

Note: Ulcers do not leave scars.

Who is at risk?

There are 2 populations particularly vulnerable to canker sores: Women; people whose parent has or has had canker sores.

Prevention of canker sores

Do you regularly have canker sores?

Here are some steps you can take to reduce the frequency of canker sores:

Have good oral hygiene

Using a soft-bristled toothbrush and floss between the teeth 1 time per day. In addition, some studies have shown a reduction in the recurrence of aphthous stomatitis in people with FMD who use antibacterial mouthwashes.15.

Avoid talking while eating and chew slowly

Indeed, it avoids injuring the oral mucosa. Indeed, the lesions make the mucous membranes more vulnerable to the appearance of canker sores.

Trying to find out if you have food intolerances or sensitivities

If necessary, remove the foods in question.

Ask your dentist for advice

If necessary, check with your dentist or denturist to ensure that the dentures you wear fit properly.

Using the right toothpaste

Avoid using sodium dodecyl sulfate toothpaste, although this is controversial.

Is there any medical treatment to treat canker sores?

How can I reduce pain?

All our tips for the treatment of the pain of aphthous stomatitis are here.

How to treat canker sores?

Canker sores usually heal on their own, so treatment is not always necessary.

If necessary, certain medications can help relieve pain.

You can use a medicated mouthwash that can relieve pain and inflammation. Some contain cortisone or prednisone, anti-inflammatories, erythromycin, an antibiotic, viscous lidocaine, a local anesthetic or diphenhydramine (Benadryl®), and an antihistamine with an anesthetic effect.

These pharmaceutical substances also accelerate the healing of canker sores and prevent them from increasing in size. They are obtained by prescription.

There are also gels, ointments, or anesthetic liquids. Several types of products are available in pharmacies, over the counter. Applied to ulcers, they protect the mucosa and relieve pain. For example, Orabase®, Oralmedic® and Zilactin®, gels made from cloves (Pansoral®).

You can use sucking tablets (Aphtoral® combining Chlorhexidine / Tetracaine / Ascorbic acid …). Other products, more concentrated, are obtained by prescription (Lidocaine gel).

Aspirin or acetaminophen tablets (Tylenol®, Acet®, Tempra®, etc.) can help calm the pain. Caution: it is better not to take nonsteroidal anti-inflammatory drugs (ibuprofen and others), which can contribute to the problem.

Some medications that were not originally intended to treat canker sores may also be beneficial. This is the case, for example, of colchicine, a drug usually used to treat gout. These drugs are taken orally in tablet form.

For a person with very severe and recurrent canker sores, other treatments, such as oral cortisone, may be used, but this is rare due to the side effects.

Finally, in case of nutrient deficiency, correcting them by taking vitamin or mineral supplements can help relieve canker sores.

If an ulcer is slow to heal, the doctor may suggest a biopsy. He then removes some tissue from the ulcer for examination under a microscope. The analysis of the tissue will determine if the lesion is of the cancerous origin or not.

More tips to reduce pain

Some additional tips that can help reduce the pain caused by canker sores:

  • put an ice cube in the mouth and let it melt on the ulcer;
  • Avoid eating foods and drinks that irritate mucous membranes. This is the case of those that are acidic (coffee, citrus fruits, pineapples, tomatoes, etc.), hard (such as toast, nuts, and pretzels), or spicy;
  • gently brush the canker sores with a little milk of magnesia a few times a day;
  • Apply a thin layer of baking soda and water to the lesion.

Finally, it is recommended to rinse your mouth with one of the following solutions and then spit it out:

  • 1 tsp baking soda and 1 tsp salt dissolved in 120 ml water;
  • 1 tbsp hydrogen peroxide in 1/2 liter of water (2 cups).

These solutions reduce pain and can be used 4 times a day.


In addition to medical treatments to treat canker sores, you can also use natural methods: aloe gel, propolis, myrrh, and licorice…

Discover below these complementary approaches, which are just as effective.

Canker sores: some complementary approaches to treat them

Aloe (Aloe vera) to treat canker sores

Three studies involving a total of 154 subjects suggest that the application of aloe gel or one of its components (acemannan) can accelerate the healing of canker sores.

Although the methodological quality of these studies is rather low, aloe gel has long been used to treat mild injuries, lesions, and inflammations of the skin because of its emollient properties.

Propolis against aphthous stomatitis

Propolis in internal use may reduce the recurrence of canker sores in people who suffer from it recurrently.

In addition, rare clinical trials indicate that propolis, in topical use, promotes the healing process of wounds and infections of the oral mucosa (gingivitis, periodontitis, abscesses, wounds, fungi).

Myrrh (Commiphora molmol)

Commission E and ESCOP recognize the effectiveness of myrrh in the treatment of inflammation of the mucous membranes of the mouth.

In India, it is part of the traditional remedies (Ayurvedic medicine) aimed at relieving mouth ulcers and gingivitis.


  • a few drops of undiluted myrrh tincture (1:5, 90% ethanol), applied to the affected parts with a cotton swab, 2 or 3 times a day;
  • 10 to 15 drops of myrrh tincture (1:5, 90% ethanol) diluted in about 30 ml of warm water, to be used as a gargle or mouthwash.

Licorice (Glycyrrhiza glabra)

Licorice has therapeutic and soothing properties that help speed up the healing of canker sores.

In the scientific literature, there are a few studies that support this traditional use, but they have been conducted with a small number of subjects and their methodological quality leaves much to be desired.

Use: Allow licorice glycyrrhizin-DGL extract tablets (containing 380 mg DGL, 4:1) to melt in the mouth.

Caution: Licorice root contains glycyrrhizin, a substance that can cause symptoms of mineralocorticoid poisoning (headache, lethargy, hypertension, water, and sodium retention, potassium hypersecretion, and sometimes even cardiac arrest).

In the case of a treatment that lasts more than 4 to 6 consecutive weeks, it is important to use deglycyrrhizated licorice (from which glycyrrhizin has been extracted).

Mind-body approaches

Mind-body approaches include a host of techniques and therapies that focus on the interactions between thoughts, emotions, psyche, and physical body.

In the case of canker sores, We recommend using this type of approach to reduce the level of stress when it is a trigger for symptoms. particularly suggests hypnotherapy and visualization.

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