Canker sores go by a number of other names as well as the main medical one of aphthous ulcers or recurrent aphthous ulcers.
These terms include aphthous stomatitis or recurrent aphthous stomatitis, aphthae and mouth ulcers.
Aphthous ulcers are easily identified in the mouth and well known, but is there anything that can be done about them? Are there times when canker sores require medical attention? This article answers these and other questions with easy-to-understand information about canker sores.
In the UK, the term "mouth ulcer" is used instead of "canker sore." When British people are talking about common mouth ulcers, they are typically referring to canker sores and not other forms of mouth ulcer such as herpetic ulcers.1
Fast facts on canker sores
Here are some key points about aphthous ulcers in the mouth. More detail and supporting information is in the article.
- Canker sores are a very common type of mouth ulcer known as aphthous ulcers
- Canker sores are typically round and less than a centimeter across, with a white or gray-yellow center surrounded by a red margin
- Common canker sores are easy to identify by their appearance under a bright light
- The main symptom of canker sores is pain at the site of the ulcer, which is irritated further by certain foods and teeth cleaning
- While risk factors are proposed, common aphthous ulcers have no clearly identified causes
- Less common types of sore do have associations with other conditions that can often be addressed, such as mouth ulcers caused by herpesvirus
- Most aphthous ulcers do not need medical attention and can be home-treated for the symptoms
- Canker sores typically heal over naturally, usually within two weeks
- More persistent, severe, numerous or particularly recurrent canker sores should be seen by a dentist or doctor.
What is a canker sore?
Canker sores, also known as aphthous ulcers, are a common oral health complaint.
A canker sore is a type of mouth ulcer known medically as an aphthous ulcer. Aphthous ulcers are one of the most common complaints of the mouth, occurring at any age but being more likely in younger adults and women.2-5
A first episode often occurs during adolescence, although children as young as 2 years may develop canker sores.3,6
Many people have only occasional aphthous ulcers. The proportion of the population affected by recurrent episodes is estimated to range between 20% and 30%.4,7-9
Causes of canker sores
Research has failed to give a scientific explanation of why canker sores develop, although there are known specific factors such as viral infection.8,10-14
The causes of recurrent cases of canker sore - known as recurrent oral aphthous ulcers or recurrent aphthous stomatitis - are also unclear, although there are correlations with a number of factors.11-14
A note for readers who use "mouth ulcers" to refer to what are canker sores: people more familiar with the canker term, such as in the US, may be referring to a broader group of lesions when they say mouth ulcers.1,8,15
Fever blisters (cold sores)
Herpes infection leading to fever blisters can sometimes affect the oral mucosa, the same lining inside the mouth affected by aphthous ulcers.
Mouth ulcers in the broader group that are not canker sores may have a specific cause - fever blisters, for example (due to the herpes virus), or other infections and conditions.1,4,8,9,15
Ulcers are sometimes associated with other conditions needing medical attention, such as inflammatory bowel disease, compromised immunity, allergies and nutritional deficiency.6,9
All cases of aphthous ulcers lack a cure for the canker sores themselves, and treatment of the ulcers is largely confined to managing the symptoms.
While there is no firm understanding of why canker sores occur, a number of factors are thought to have some involvement, including:9,11-14
- Hormonal changes
- Physical trauma (damage to the lining of the mouth, such as during dental treatment)
- Food hypersensitivity
- Nutritional deficiencies, including of iron, folic acid or vitamin B12
A report by the US Surgeon General cites up to a quarter of the general population being affected by recurrent aphthous ulcers, noting there may be higher numbers among selected groups, such as health professional students.9
Symptoms of canker sores
Canker sores have clear features. The lesions cause local pain and can be easily irritated.
There are otherwise no further symptoms in simple cases, although the pain may cause feelings of being fed up with the mouth ulcer.
Common features of canker sores include them being:4-7,9,10,14,16,17
- Usually well-defined, round, smaller than a centimeter across, and usually shallow in the mouth's lining, its mucosal surface
- White or yellow-gray center surrounded by an inflammatory red margin
- In medical terms, this means an 'erythematous halo' is seen around a fibrinous "pseudomembrane" formed over the mucosal ulceration (eruption/destruction)
- Often fading to gray over time
- Usually in the front part of the mouth, on its floor, inside of the lip (labial mouth), inside of the cheeks (buccal), or under the front or sides of the tongue
- Sometimes affecting the gums and, relatively uncommonly, the surface of the back part of the mouth
- Persistent for typically a week or two before healing.
When to see a doctor about canker sores
Common canker sores usually heal without the need for medical treatment. More severe or recurrent cases may be eased by prescribed treatments, although these do not "cure" such ulcers.
If canker sores persist without improvement for more than 2 weeks, a health care professional should be consulted.
Sometimes mouth ulcers are associated with other conditions that require medical attention. Examples are inflammatory bowel disease, compromised immunity, allergies and nutritional deficiency.6,9
As a general guide, canker sores should be brought to the attention of a dentist or doctor when they:2,10
- Persist for more than 2 weeks without improvement
- Get worse - including while being treated with home remedies
- Recur often - 2 to 3 times a year or more - or are particularly numerous or severe
- Are accompanied by other symptoms, such as fever, diarrhea, headache or skin rash
- Come with any concern at all that another condition may be related to them.
On the next page, we look at treatment and prevention of canker sores.