Canker sore


Canker sores, also known as aphthous ulcers, are small lesions that develop on the soft tissues in your mouth or at the base of your gums. Unlike cold sores, they do not occur on the surface of your lips and are not contagious. While they can be painful and make eating and talking difficult, most canker sores are typically very small, measuring less than 1 millimeter in size. In some cases, they may grow to be 1/2 inch to 1 inch in diameter.
There are two types of canker sores: simple canker sores and complex canker sores. Simple canker sores tend to appear a few times a year and usually last up to a week. On the other hand, complex canker sores are less common and occur more frequently in individuals who have previously experienced them.

Fortunately, most canker sores heal on their own within a week or two. However, it is advisable to consult with your doctor or dentist if you have unusually large or painful canker sores, or if the sores do not seem to heal.


Canker sores often have a circular or oval shape, featuring a white or yellow center surrounded by a red border. They typically develop inside the mouth, either on or beneath the tongue, inside the cheeks or lips, at the gum line, or on the soft palate. It is common to experience a tingling or burning sensation a day or two prior to the appearance of the sores.

Minor canker sores

The most typical canker sore:

  • Normally appears small
  • Has a shape like an oval with red borders
  • Recover in one to two weeks without scarring

Major canker sores

Major canker sores are less frequent, and:

  • May be very painful
  • Can leave significant scars and take up to six weeks to cure.
  • Are deeper than minor canker sores and greater in size.
  • Are typically rounded with clearly defined borders, but when very large, they may have irregular edges.

Herpetiform canker sores

Herpetiform canker sores are infrequent and typically emerge during later stages of life, yet they do not result from an infection with the herpes virus. These particular canker sores:

  • Irregular edges
  • Sizes that appear like dots
  • In one to two weeks, recover without scars
  • Frequently appear in groups of 10 to 100 ulcers, but may merge into one large ulcer

If you experience unusually large canker sores, recurring or frequent outbreaks with new sores developing before old ones heal, persistent sores lasting two weeks or more, sores extending into the lips, uncontrollable pain, extreme difficulty eating or drinking, high fever along with canker sores, or if sharp tooth surfaces or dental appliances trigger the sores, it is advisable to consult your doctor or dentist for further evaluation and appropriate care.


Although the exact etiology of canker sores is still unknown, researchers believe that a number of circumstances, even within the same person, can induce outbreaks.

Canker sores can be triggered by various factors, including:

  • Oral trauma caused by dental procedures, aggressive brushing, sports accidents, or unintentional cheek biting.
  • Use of toothpastes and mouth rinses containing sodium lauryl sulfate.
  • Food sensitivities, especially to chocolate, coffee, strawberries, eggs, nuts, cheese, and spicy or acidic foods.
  • Inadequate intake of essential nutrients like vitamin B-12, zinc, folate (folic acid), or iron.
  • Allergic reaction to specific bacteria present in the mouth.
  • Infection with Helicobacter pylori, the bacteria responsible for peptic ulcers.
  • Hormonal fluctuations during menstruation.
  • Emotional stress.

Canker sores can be associated with various conditions and diseases, including:

  • Celiac disease: This is a digestive disorder caused by a sensitivity to gluten, a protein commonly found in grains.
  • Inflammatory bowel diseases: Conditions like Crohn’s disease and ulcerative colitis, which cause inflammation in the digestive tract, can also contribute to the occurrence of canker sores.
  • Behcet’s disease: A rare disorder characterized by widespread inflammation in the body, including the mouth, can lead to the development of canker sores.
  • Abnormal immune response: Sometimes, the immune system mistakenly targets healthy cells in the mouth instead of fighting off pathogens like viruses and bacteria. This malfunction can result in canker sores.
  • HIV/AIDS: The human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) can weaken the immune system, making individuals more susceptible to canker sores.

Risk factors

Canker sores can develop in anyone, but they are more frequently observed in teenagers and young adults, particularly in females. They are most found in individuals in their teens and twenties, and women and those assigned female at birth are more prone to experiencing them compared to men and those assigned male at birth. Hormonal changes are believed to play a role in this gender difference. Additionally, individuals with a family history of canker sores often experience recurring episodes, possibly due to hereditary factors or shared environmental triggers such as specific foods or allergens.