What Is Canker Sore and What Causes It?

What is canker sore and what causes it?

Canker sores, also called aphthous ulcers, are small, shallow lesions that develop on the soft tissues in your mouth or at the base of your gums.

Canker sores don’t occur on the surface of your lips and they aren’t contagious. They can be painful, however, and can make eating and talking difficult.

The precise cause of canker sores remains unclear.

The most common triggers for canker sores include:

  • Food sensitivities, particularly to chocolate, coffee, strawberries, eggs, nuts, cheese, and spicy or acidic foods
  • A minor injury to your mouth from dental work, overzealous brushing, sports mishaps or an accidental cheek bite
  • Toothpastes and mouth rinses containing sodium lauryl sulfate
  • A diet lacking in vitamin B-12, zinc, folate (folic acid) or iron

Certain conditions and diseases may cause canker sores, such as:

  • Celiac disease,
  • Behcet’s disease,
  • A faulty immune system
  • HIV/AIDS, which suppresses the immune system

Most canker sores go away on their own in a week or two. Check with your doctor or dentist if you have unusually large or painful canker sores or canker sores that don’t seem to heal.


* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.