What is a Canker Sore?

Many people often wonder exactly what are canker sores?
Canker sores, also known as Aphthous Ulcers, are small lesions that occur inside the mouth, and are not contagious.


One to two days before appearing, a burning or tingling sensation may be present in the area of the mouth where the lesion is developing. Rarely, a fever might present itself when developing a canker sore.
Canker sores appear inside the mouth as round or oval sores typically with a red border and yellow or white center. Canker sores typically develop:
On the top surface of the tongue and the tip of the tongue
Underneath the tongue, on the floor of the mouth
The inside of the cheek and lip
On the gum tissue
Canker sores do not develop on the external surfaces of the lips and are not to be confused with cold sores.

Types of Canker Sores

Canker sores may be classified as:
Minor – Although painful, minor canker sores are often fully healed within two weeks after onset. The size of a minor canker sore varies, but typically stays under 1/3 inch to 1/2 inch.
Major – Canker sores that appear larger that 1/3 inch to 1/2 inch, last longer than two weeks, and appear to have irregular margins — oddly shaped — may be classified as major. Rarely, this type of canker sore may leave behind a scar. Common in immunosuppressed patients.
Herpetiform Canker Sores – A cluster of several tiny lesions that appear to form one larger sore. This type of canker sore may last from one week to one month.

Canker sores may become painful, especially when eating, drinking, and talking.
The cause of canker sore development varies from person to person, with an exact cause unknown.
Treatments for canker sores also vary depending on the suspected cause.
It is recommended that you seek treatment from your dentist if you have recurrent canker sores and/or canker sores that do not heal after 14 days.
Also Known As:
Aphthous Ulcers
Common Misspellings:
Kanker sores