Aphthous Ulcers (canker sores)

Aphthous ulcers, also known as canker sores, are small lesions (usually 1 to 2 mm in diameter) that appear on the inner surface of the cheeks and lips, on or under the tongue, and, more rarely, on the gums or palate. They are small, crater-like sores that are white or yellowish in colour, surrounded by a red border. Canker sores are more prevalent in women, individuals under the age of 40 years, Caucasians and non-smokers. They are not contagious.

There are various types of canker sores:

Simple canker sores
These sores are usually the result of accidental trauma, tend to appear only one at a time, and heal spontaneously within 7 to 14 days. Some simple canker sores can be very large (in excess of 1 cm in diameter). They are often accompanied by fever and may leave a scar. These types of sores are much more bothersome and take longer to heal.

Recurrent canker sores
Five and even up to 10 of these ulcers can develop at one time throughout the mouth. Although they share the same characteristics as simple canker sores, a number of factors can play a role in triggering an outbreak. Factors that promote recurrence may be linked to heredity, stress, immunity and hormonal changes in women.

Herpetiform ulcers
Some diseases produce aphthous ulcers that are found not only in the mouth, but on the genitals, in the eyes and on the skin. Individuals who develop recurrent canker sores on more than one area of the body should consult a doctor.


There are many factors thought to promote the development of canker sores:

  • Allergies or sensitivity to certain foods such as citrus, pineapple, chocolate, dried fruit, nuts, spicy foods, vinegar, acidic foods, etc. (varies from one person to another)
  • Injury or irritation (aggressive teeth brushing, dental appliances, dentures, etc.)
  • Folic acid, iron and/or vitamin B12 deficiency
  • Quitting smoking
  • Hormonal changes (puberty, pregnancy, menopause, menstrual cycle)
  • Fatigue, stress
  • Symptoms associated with certain diseases (diabetes, Behcet's disease, inflammatory bowel diseases) or viral infections (HIV, varicella, zona)


Canker sores can be uncomfortable and extremely painful, particularly when eating. Some also experience a burning or tingling sensation 24 hours before the sore becomes visible.


Canker sores may take 10 to 20 days to heal, while large ulcers can take up to 2 months. If a sore does not heal after a few weeks, if you have them on more than one part of your body, or if they reoccur very frequently, it is important that you see a doctor. You should also see a doctor if you have a canker sore and develop fever, red eyes, joint pain or diarrhea (as it may be indicative of another disease).

To alleviate the pain associated with canker sores, try to avoid eating foods that are hard (ex: toast, chips, nuts), acidic (ex: citrus, soft drinks), irritating (ex: chocolate, coffee, alcohol), and either very salty or very spicy. Melting an ice cube on the ulcer may provide some relief. To promote healing, you can also prepare a homemade solution to gargle with, 4 times a day: 1 teaspoon of salt and 1 teaspoon of baking soda in 250 ml of water. Treatment mainly consists in alleviating the pain. That said, prescription and over-the-counter mouthwash, creams and ointments are available. Speak to your pharmacist, as he or she will be able to advise you on the product best suited for your particular needs.

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