Canker Sores: Symptoms & treatment

The sores are small ulcers superficial that form most often on the mucous membranes inside the mouth  : on the inside of the cheeks, tongue, the inside of the lips, palate or gums. Canker sores can also appear on the genitals, but rarely. This will only deal with canker sores in the mouth.

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

The mouth sores are common: about 17% of the population is affected at some point in his life. Often the first outbreak of canker sores appears during childhood . Then, the symptoms return at certain times, and then disappear permanently during the thirties.

Canker sores can manifest themselves in a number of ways.

  • Minor form  : 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 appear in this form in 80% of cases.
  • Major or bothersome form  : larger ulcers (more than 1 cm in diameter), with an irregular outline, which can take 6 weeks to heal and often leave scarring.
  • Herpetiform or miliary form  : 10 to 100 tiny ulcers (less than 3 mm in diameter) with irregular contours which gradually regroup, then form an ulcerative area, which persists for 1 to 2 weeks without leaving a scar.


The pain usually lasts 2 to 5 days. However, ulcers may take 1 to 3 weeks to heal.


A canker sore is a painful round or oval wound that occurs in flare-ups.

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

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

When symptoms resembling those of mouth ulcers recur , it is best to consult a doctor . He 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 .

Canker-like ulcers can be caused by a chronic disease , 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. People with weakened immune systems (due to HIV infection or cancer treatment, for example) are more likely to have ulcers which could be mistaken for canker sores.


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 be contributing to this.

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However, scientists have noted factors that tend to trigger symptoms in people with the condition .

  • A small wound inside the mouth. It can be caused by a bad fit of a dental prosthesis, by oral surgery, by too forceful use of the toothbrush, by biting the cheek, etc.
  • Physical fatigue and stress These often precede the onset of canker sores.
  • Food allergies or sensitivities. There is a link in the scientific literature between the recurrence of canker sores and 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 of vitamin B12, zinc, folic acid or iron.
  • Smoking cessation. Canker sores can occur during smoking cessation.
  • An infection with the bacteria Helicobacter pylori , the same bacteria that can cause an ulcer in the stomach or small intestine.
  • Certain drugs. Nonsteroidal anti-inflammatory drugs (ibuprofen and others), beta blockers (propranolol and others) and alendronate (against osteoporosis) can cause canker sores.
  • Hormonal changes related to the menstrual cycle , possibly. Canker sores tend to appear during menstruation, but this link is uncertain.

Remark. Using a toothpaste that contains sodium dodecyl sulfate (called sodium lauryl sulfate ), an ingredient found in most toothpastes, could increase your risk of getting 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 sores 5-7 . However, a more recent clinical trial concluded that the type of toothpaste used did not influence canker sores 8.

Symptoms, people at risk and prevention of canker sores

Symptoms of canker sores

The canker sore outbreak is often preceded by a tingling sensation in the affected area.

  • One or more small ulcers inside the mouth. The center of the ulcers is whitish, and their outline is red.
  • Canker sores cause a sharp pain comparable to a burning sensation (by the way, the word canker sore comes from the Greek aptein , which means “to burn”). The pain is accentuated when we talk or when we eat, especially during the first few days.

Remarks . Ulcers do not leave scars.

People at risk

  • The women.
  • People whose parent has or has had canker sores.

Prevention of canker sores

Measures to reduce the frequency of canker sores

Have good oral hygiene . Use a soft-bristled toothbrush . Floss between teeth once a day. In addition, some studies have shown a reduction in recurrence of aphthous stomatitis in sufferers who use antibacterial mouthwashes 15 .
Avoid speaking while eating and chewing slowly so as not to injure the oral mucosa. The lesions make the mucous membranes more vulnerable to the appearance of canker sores.
Try to find out if you have food intolerances or sensitivities and, if necessary, remove the foods in question.
If necessary, check with your dentist or denturist that the dental prostheses you wear are properly adjusted.
Avoid using sodium dodecyl sulfate toothpaste, although this is controversial.

Medical treatments for canker sores

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

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If needed, certain medications can help relieve the pain.

  • mouthwash medication can relieve pain and inflammation . Some contain cortisone or prednisone, anti-inflammatory drugs, erythromycin, an antibiotic, viscous lidocaine, a local anesthetic or diphenhydramine (Benadryl®), an antihistamine with an anesthetic effect. These pharmaceutical substances also accelerate the healing of canker sores and prevent them from increasing in size. They can be obtained by prescription.
  • An anesthetic gel , ointment or liquid . Several types of products are found in pharmacies, over the counter. Applied to ulcers, they protect the mucous membrane and relieve pain. For example, Orabase®, Oralmedic® and Zilactin®, clove-based gels (Pansoral®). You can also use tablets to suck (Aphtoral® combining Chlorhexidine / Tetracaine / Ascorbic acid). Other, more concentrated products can be obtained by prescription (Lidocaine gel). Other, more concentrated products can be obtained by prescription.
  • Tablets of aspirin or acetaminophen (Tylenol®, Acet®, Tempra, etc.) can also help relieve pain.
    Be careful . It is better not to take nonsteroidal anti-inflammatory drugs (ibuprofen and others), which can contribute to the problem.
  • Some medicines that were not originally intended to treat canker sores may be of benefit. This is the case, for example, with colchicine (a medicine usually used to treat gout). These drugs are taken orally in tablet form.
  • For someone with very severe and recurring canker sores, other treatments, such as oral cortisone , may be used , but this is rare given the side effects.
  • If nutrient deficiency, corrected by taking supplements of vitamins or minerals .

If an ulcer is slow to heal, your doctor may suggest a biopsy. He then takes some tissue from the ulcer in order to examine it under a microscope. Analysis of the tissue will determine whether the lesion is cancerous or not.

Other tips for reducing pain

  • Put an ice cube in your mouth and let it melt on the ulcer.
  • Avoid consuming foods and drinks that irritate the mucous membranes. This is the case with those that are acidic (coffee, citrus, pineapple, tomatoes, etc.), hard (like toast, nuts and pretzels) or spicy.
  • If rinse the mouth with one of the solutions following, and then spit it out:
    – 1 tbsp. baking soda and 1 tsp. of salt dissolved in 120 ml of water.
    – 1 C. of hydrogen peroxide in ½ liter of water (2 cups).
    These solutions reduce pain 9 . Use 4 times a day if possible.
  • 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 paste to the lesion .
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Canker sores – Our doctor’s opinion

Most people do not see a doctor for canker sores and take care of themselves. This is very good.

However, for people who have frequent recurrences of canker sores (a minority), a medical examination and a blood test are necessary. This makes it possible to search for another disease which could cause canker sores, such as those mentioned in this document (Crohn’s disease, Behçet’s disease, etc.).

In addition, in the case of rebellious and persistent ulcerations which could be something other than a simple mouth ulcer, a biopsy should be carried out. Fortunately, this rarely happens.

Complementary approaches to canker sores

Aloe ( Aloe vera ). Three studies involving a total of 154 subjects suggest that applying aloe gel or one of its components (acemannan) can speed up healing of canker sores 10 , 11 . However, the methodological quality of these studies is rather low. Aloe gel has long been used to treat minor wounds, lesions and inflammation of the skin due to its emollient properties .

Propolis . Propolis used internally may reduce the recurrence of canker sores in people who have it repeatedly 20 . In addition, rare clinical trials indicate that propolis, when used topically, promotes the healing process of wounds and infections of the oral mucosa (gingivitis, periodontitis, abscesses, wounds, fungi)

Myrrh ( Commiphora molmol ). The Commission E and ESCOP recognize the effectiveness of myrrh in the treatment of mucositis of the mouth. In India, it is one of the traditional remedies (Ayurvedic medicine) aimed at relieving mouth ulcers and gingivitis.
– A few drops of myrrh tincture (1: 5, 90% ethanol) undiluted, applied to the affected areas with a cotton swab, 2 or 3 times a day.
– From 10 to 15 drops of tincture of myrrh (1: 5, 90% ethanol) diluted in about 30 ml of lukewarm water; to use as a gargle or as a mouthwash.

Licorice ( Glycyrrhixa glabra ). Licorice has therapeutic and soothing properties that accelerate the healing of canker sores. In the scientific literature, there are a few studies that support this traditional use, but they were conducted with a small number of subjects and their methodological quality leaves much to be desired 12 .
Dissolve deglycyrrhizinated-DGL liquorice extract tablets in your mouth (containing 380 mg of DGL, 4: 1).
Licorice root contains glycyrrhizin, a substance that can cause symptoms of mineralocorticoid poisoning: headache, lethargy, high blood pressure, water and sodium retention, hypersecretion of potassium, and sometimes even cardiac arrest. In the case of a treatment that lasts longer than 4 to 6 consecutive weeks, it is important to use deglycyrrhized licorice (from which glycyrrhizin has been extracted).

Body-mind approaches. We group together under the name of body-mind approaches a host of techniques and therapies that focus on the interactions between thoughts, emotions, the psyche and the physical body. In case of canker sores, Dr.  Andrew Weil recommends using this type of approach to reduce the level of stress when it is a trigger for symptoms. It more particularly suggests hypnotherapy and visualization 14 .