About Canker Sores

Canker sores (aphthous stomatititis) are small, shallow ulcers characterized as non-malignant, non-contagious, and non-sexually transmitted sores within the oral cavity. Their appearance is of a round or elongated ulcer with a yellow, white, or grey floor surrounded by a reddened halo. Canker sores occur as superficial lesions within the mouth, specifically on the oral mucosa of the floor of the mouth, cheeks, and vestibule and are sometimes concentrated towards the anterior portion of the mouth.

The most common form of canker sores have a diameter of less than 10 mm, occur in multiples of 1 to 5 ulcers, and lasts for 7 to 14 days with a 3-month recurrence rate. They initially appear in childhood and adolescence, affect up to 25% of the general population, and are more common in females. These ulcers cure spontaneously and the time between ulcer recurrences is variable.

Differences From Cold Sores

Canker sores are distinct from cold sores. Cold sores, termed fever blisters and herpes virus type 1 blisters, are lesions caused by viral infection, occur as fluid-filled vesicles which are painful, highly contagious, and are often found outside the mouth. Canker sores are found inside the mouth.


The cause of canker sores is unknown, but apparently involves an immunological aspect activated by the type of white blood cell termed a cytotoxic T-cell lymphocyte (“T-cells”). An ulcer results from the destruction of the mucosa (i.e., the surface, moist lining of the inner mouth and tongue) mediated through a T-cell mediated immune response. The trigger for this response is not known yet and is considered a multifactorial. Although there is some aspect of genetic predisposition, other factors that may trigger ulcer formation include nutritional deficiencies (e.g., of vitamin B12 and folic acid), allergic reactions to certain foods (e.g., tomatoes), sensitivity to commercial chemicals (e.g., sodium lauryl sulfate present in some brands of toothpaste), emotional stress, any trauma, and abrasion by dental appliances (e.g., braces).


As these ulcers are self-limiting (i.e., the lesions will go away by themselves), treatment focuses on reducing pain, healing time, and lowering frequency of recurrence. Pain is most intense on the days immediately following the emergence of the ulcer and subsequently subsides as the healing process progresses; no scarring is evident. For most, the pain is tolerable and dietary modification may be suggested, such as the avoidance of spicy foods, citric and acidic foods and beverages. Some cases of canker sores may require the need for topical anesthetics to reduce pain and therapeutic mouthwashes to decrease the number of ulcer days. Vitamin B12 may also be helpful in treating canker sores. Some cases of canker sores may require seeing the dentist for appropriate medications and topical medicaments. Use of a dental soft tissue laser can quickly lessen the discomfort by sealing off nerve endings and can promote faster healing.