Canker Sores: Causes, Remedies and Prevention
June 24, 2016 at 3:31 PM
Written by Markus MacGill
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.
Contents of this article:
1. What is a canker sore?
2. Treatments and prevention
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?
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.
A first episode often occurs during adolescence, although children as young as 2 years may develop canker sores.
Many people have only occasional aphthous ulcers. The proportion of the population affected by recurrent episodes is estimated to range between 20% and 30%.
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.
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.
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.
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.
Ulcers are sometimes associated with other conditions needing medical attention, such as inflammatory bowel disease, compromised immunity, allergies and nutritional deficiency.
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:
- 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.
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:
- 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.
Sometimes mouth ulcers are associated with other conditions that require medical attention. Examples are inflammatory bowel disease, compromised immunity, allergies and nutritional deficiency.
As a general guide, canker sores should be brought to the attention of a dentist or doctor when they:
- 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.
Treatments for canker sores
The good news is that the pain and discomfort of canker sores can be reduced by readily available prescription and non-prescription treatments and home remedies.
Simple cases of occasional canker sores are self-limiting; they will heal over and disappear without intervention.
No remedies are proven to change the course of aphthous ulcers themselves or the recurrence of the condition - treatments mostly just reduce pain, discomfort and complication.
Few treatments marketed for aphthous ulcers have been the subject of robust clinical testing.
When the sores are not associated with other conditions, science has so far failed to explain what causes them, and their management is focused on treating symptoms, reducing inflammation, and promoting the healing process by countering secondary effects that could slow this down, such as bacterial involvement.
Home remedies for canker sores
Even before reaching for any one of a large array of pain-relieving mouthwashes, gels or tinctures that can be bought from stores, one home remedy that may be possible with items already perhaps in the bathroom cabinet has been suggested by the US Library of Medicine.
This procedure can be followed three or four times a day:
- Rinse with mild, over-the-counter mouthwash or salt water (with either, do not swallow)
- Make a mixture that is half hydrogen peroxide and half water
- Use a cotton swab to apply some of the mixture directly to the sore
- Finally, dab a small amount of milk of magnesia on the canker.
So-called alternative therapies may be worth trying at home. A review of the management of aphthous ulcers written for the journal American Family Physician, published in 2000, listed a number of options, although it noted that there had been no randomized controlled trials to robustly test safety and efficacy:
- Anecdotes of relief and better healing from sucking on zinc gluconate lozenges (sold for the common cold)
- Vitamin C, vitamin B complex and lysine "may speed healing when taken orally at the onset of lesions"
- Sage and chamomile mouthwash 4-6 times a day may help - infuse equal parts of the two herbs in water
- Echinacea (herbaceous flowering plant) may have an immune modulatory effect to reportedly speed healing
- Carrot, celery and cantaloupe juices "have been reported as helpful."
Prescription therapies for canker sores
As mentioned at the beginning of this section on treatments, most aphthous ulcers are self-limiting, eventually healing without intervention. Treatment can only ease the pain and irritation, and help prevent complication.
More severe or persistent cases of canker sores need to be checked by a doctor to rule out associated conditions (such as inflammatory bowel disease, compromised immunity, allergies and nutritional deficiency) or to access prescription treatments. Again, any treatments aimed at the ulcers themselves are not certain to change their course but can ease the symptoms.6,9
Antibiotics such as tetracycline may be prescribed to minimize inflammatory irritation by preventing bacterial aggravation.
Anesthetics, as well as being available in consumer products for canker sores, may also be prescribed as topical preparations to ease irritation and pain.
Other prescription treatments that may be used against problematic canker sores are tried empirically - without firm evidence, that is, but with the aim of seeing if they might help based on a theory (and assuming the safety considerations of prescribing the remedy).
The American Academy of Oral & Maxillofacial Pathology, for example, cites an association between recurrent cases of aphthous ulcers and an overactive immune system, so topical suppressant medications may help, such as locally applied cortisone.
With a similar mode - and again with limited evidence against aphthous ulcers - topical corticosteroids are a class of drugs often considered by doctors, including clobetasol ointment, dexamethasone rinse, fluocinonide gel (Lidex) and triamcinolone (Kenalog - in Orabase paste).
Side effects are an important consideration with prescription drugs, and doctors should help with weighing these up when considering any potential benefit in the more difficult cases of canker sores.
One possible side effect of using corticosteroids against canker sores is a fungal infection in the mouth.
Particularly severe or recurrent cases of aphthous ulcers may be referred to oral specialists, who may consider systemic rather than locally applied (topical) drugs. These specialists may also be needed to make a more specific diagnosis - some rare cases of recurrent aphthous ulcers are diagnosed as Sutton disease, for example.
Prevention of canker sores
The question of what can be done to prevent canker sores in the first place has no clear answer. However, there are ways to prevent aphthous ulcers from getting or feeling worse.
Prevent aggravation of aphthous sores by avoiding:
- Abrasive foods or those that can stick in the mouth (potato chips, for example)
- Spicy, acidic or hot foods and drinks
- Traumatizing the ulcers (through harsh contact with toothbrush bristles, for example).