Medically reviewed by Dr. A.M. van Coevorden, dermatologist
Aphthous ulcerspainful mouth ulcers that heal on their own
Aphthous ulcers, also known as canker sores, are painful, shallow ulcers on the lining of the mouth that heal on their own and tend to come back. About one in five people experience them at some point, often first around puberty. In most people they stay small and clear up within one to two weeks.
What are aphthous ulcers?
Aphthous ulcers are painful ulcers of the mouth lining that often first appear around puberty and tend to recur. They affect about 20% of the population. Most people have occasional small, painful ulcers that heal on their own within one to two weeks. Some people have frequently recurring, large and very painful ulcers. Several factors probably play a role in how they develop. In about 10% of people with aphthous ulcers a cause is found. In all other cases the condition can be treated when needed, but not permanently cured.
How do you get aphthous ulcers?
There is no single cause. Various factors probably trigger ulcers in people who are prone to them. Most people with small ulcers are otherwise healthy, but large ulcers can point to other illnesses.
Trigger factors:
- Damage to the mouth lining, for example from brushing, flossing, chewing gum, sharp pieces of food, a poorly fitting denture, injections or dental treatment. Smoking also damages the mouth lining.
- Emotional stress, considered an important trigger.
- Hormonal factors. A clear link with menstruation has never been proven, although ulcers sometimes disappear while using the contraceptive pill or during pregnancy.
- Viruses and bacteria were once considered a cause, but this has never been proven. The herpes virus that causes cold sores plays no role in aphthous ulcers. They are not contagious.
- Hereditary predisposition probably plays a role. Others in the family often have them too.
- Food hypersensitivity is mentioned but never proven. Occasionally a reaction to food cannot be ruled out.
- Medicines that suppress the immune system and certain painkillers such as ibuprofen and aspirin can cause ulcer-like sores.
Large ulcers in particular can be a sign of an underlying illness, such as Behçet's disease, blood disorders from a lack of iron, vitamin B12 or folic acid, and bowel diseases such as coeliac disease, Crohn's disease and ulcerative colitis. People with HIV can also develop ulcer-like sores in the mouth.
Are aphthous ulcers contagious?
No. They are not caused by a virus or bacterium and cannot be passed from person to person.
What are the symptoms?
Aphthous ulcers are painful, shallow, round to oval, grey-white ulcers with a red border. They mostly appear on the underside of the tongue, the floor of the mouth, the cheek lining, the inside of the lip, the soft palate and sometimes the throat. There are small and large ulcers. Small ulcers are the most common (90%): less than half a centimetre, moderately painful, and usually healing within one to two weeks without a scar. Large ulcers look the same but are more than a centimetre across and deeper. They heal slowly over many weeks and leave a scar. Large ulcers can cause severe pain, fever and general illness, and sometimes occur together with ulcers on the genitals or around the anus.
How is the diagnosis made?
The doctor usually makes the diagnosis easily from the symptoms and appearance. Most patients are young, healthy people who need no further tests. The doctor will ask about possible trigger factors and about symptoms that might point to an underlying illness. Occasionally a blood test follows, or a small piece of the lining is removed under local anaesthetic for examination.
What is the treatment?
If a trigger or underlying illness is found, treatment focuses on that. In about nine out of ten people the cause stays unknown and only symptomatic treatment is possible: relieving pain, shortening the episode and reducing the number of new ulcers. Treatment is often difficult.
Local treatments: pain can be reduced with lidocaine gel. Small ulcers can be treated with corticosteroids, preferably in a base made for the mouth lining, applied three to four times a day. A tetracycline mouthwash, rinsing for five minutes four to five times a day, is an alternative, as is rinsing with chlorhexidine.
Systemic treatments (tablets) are used only for severe, persistent ulcers that do not respond enough to local therapy, usually prednisone in a short course. During the course there are few or no ulcers, but the condition usually returns after stopping.
What can you do yourself?
Try to identify factors that seem to trigger the ulcers and avoid them. Be careful when brushing and flossing so you do not create small wounds in the mouth lining.
What is the outlook?
In most people there is no identifiable cause and new ulcers appear from time to time, sometimes for many years. Their number and severity usually decrease over the years. In about 10% a trigger or illness is found; if it can be resolved, the ulcers often reduce or disappear.
Frequently asked questions about aphthous ulcers
Are aphthous ulcers contagious?
No. They are not caused by a virus or bacterium and cannot be passed from person to person.
How long do they last?
Small ulcers usually heal on their own within one to two weeks, without a scar. Large ulcers take longer and can leave a scar.
Where do they come from?
In about nine out of ten people the cause stays unknown. Triggers include damage to the mouth lining, stress and certain medicines.
Can I do anything myself?
Yes. Avoid factors that seem to trigger them and be careful when brushing and flossing to prevent small wounds.
When should I see a doctor?
Large, very painful or long-lasting ulcers, ulcers with fever or general illness, or ulcers that keep returning are worth having assessed to rule out an underlying cause.