Canker sores

Other Names:
Aphthous ulcer

A canker sore (aphthous ulcer) is a common form of mouth ulcer. It is a benign open sore in the mouth, which appears as a painful white or yellow sore (ulcer) surrounded by a bright red area. The cause is unknown.


There may be an inherited predisposition to the development of canker sores. There may also be an immune system link. Ulcers may develop in response to mouth injury such as dental procedures or aggressive tooth cleaning. They are also triggered by stress, dietary deficiencies (especially iron, folic acid, or vitamin B12), menstrual periods, hormonal changes, food allergies, and similar situations. They may occur with no identifiable cause. Canker sores usually appear on nonkeratinized mouth tissue including the inner surface of the cheeks and lips, tongue, soft palate, and the base of the gums. They usually begin with a tingling or burning sensation, followed by a red spot or bump that ulcerates. Pain spontaneously decreases in 7 to 10 days, with complete healing in 1 to 3 weeks. Occasionally, a severe occurrence may be accompanied by nonspecific symptoms of illness such as fever or malaise. Recurrence is common and may continue for years.


Canker sores occur in women more often than men. They may occur at any age, but usually first appear between the ages of 10 and 40.

There are multiple types of canker sores:

Minor or Simple Canker Sores (Minor Aphthous Stomatitis)

This type of canker sore is arguably the most common, affecting more than 80 percent of people with the condition. Minor canker sores are very small, oval-shaped with a red border and measure less than 1 centimeter in diameter.  Most people usually have no more than three to four episodes of minor canker sores in a year. Compared to other types of sores, minor canker sores heal the fastest, with recovery time taking only about one week, without any form of scarring.

Major Canker Sores (Major Aphthous Stomatitis)

Major canker sores are less common, since only 15 percent of patients with the condition experience these. Compared to minor canker sores, these are deeper and larger, measuring over 1 centimeter in diameter. The sores are round with either defined edges or irregular borders, especially if it’s a large lesion. Major canker sores are extremely painful and take a longer time to heal. The typical recovery time for these sores takes at least six weeks, and they could cause scarring in the mouth. In some cases, these sores can even transform the shape of the mucosal surface.

Herpetiform Canker Sores (Apthous Stomatitis)

Of these types of canker sores, herpetiform canker sores are the least common, since these are only present in less than 5 percent of people. These sores typically occur in older people; contrary to popular belief, they are not caused by the herpes virus.  Herpetiform canker sores start off as irregular-edged clusters of 10 to 100 very small lesions, with some measuring less than 1 millimeter. As time progresses, the clusters could merge together to form larger groups. While the appearance of these clusters could be alarming, they tend to heal fast. It takes just over one to two weeks for herpetiform canker sores to heal, without any scarring.

Broader Problems:
Aphthous stomatitis
Related Problems:
Medicine Pathology
Related UN Sustainable Development Goals:
GOAL 3: Good Health and Well-being
Problem Type:
G: Very specific problems
Date of last update
24.06.2019 – 20:55 CEST