What is it?
A mouth ulcer is a round or oval sore that appears on the movable, soft lining inside the mouth. The middle is covered by a whitish yellow film, with a clear red ring around it. The inside of the cheek and lip, the edge of the tongue, under the tongue and the soft areas at the entrance to the throat are the typical places.
Recurrent mouth ulcers means these sores appearing several times a year or more often. An ulcer is not an infection; it does not pass from person to person and it is different from a cold sore, which is linked to a virus. Sores on firm, hard-surfaced areas such as the hard palate, the ridge of the gum and the outer edge of the lip are usually not regarded as aphthous ulcers.
An ulcer usually starts with burning and stinging on the first day, is at its most painful within a few days and then eases. Small ulcers are expected to heal within one to two weeks without leaving a scar. Where the sores keep coming back, are larger than usual or last a long time, an underlying cause is looked for.
Signs
You will not necessarily have all of these at once.
Why does it happen?
- 01
Mechanical and chemical irritation
Biting your cheek, brushing hard, a sharp edge on a tooth or a poorly fitting denture can damage the lining and start an ulcer. Toothpastes containing sodium lauryl sulfate have been reported to increase recurrences in some people.
- 02
Personal predisposition and trigger periods
In most people the tendency to ulcers follows a family pattern. Recurrences are often described as becoming more frequent during times of heavy stress, poor sleep and hormonal change.
- 03
Deficiencies and causes elsewhere in the body
Iron, B12 and folate deficiency, coeliac and bowel diseases, and some conditions involving the immune system can lie behind ulcers that keep coming back. These causes can only be assessed with the tests a doctor will ask for.
- 04
Certain foods and medicines
Foods such as walnuts, chocolate, tomatoes and citrus fruits have been reported as triggers in some people; this link varies from person to person. Some medicines can also produce similar sores in the mouth.
How does it progress?
- Minor
Small ulcer
This is the most common type. It is usually less than a centimetre across, appears singly or in small numbers, and is expected to heal within one to two weeks without leaving a scar.
- Major
Large ulcer
It is wider, deeper and more painful. Healing can take weeks and it can leave a scar where it heals. With this type, assessment by a dentist and telling it apart from other conditions become more important.
- Herpetiform
Many small sores
A large number of pinhead-sized sores appear together and can merge into wider areas. Despite the name it has nothing to do with cold sores; it is not a viral infection.
How is it treated?
No treatment has been described that prevents mouth ulcers altogether. The aim is to reduce the pain, help healing along and remove the causes that might make recurrences less frequent. The dentist first assesses whether the sore really is an aphthous ulcer, going by where it is and how it looks; cold sores, sores caused by injury and other conditions of the lining are separated out.
The first thing that can be done at the clinic is to remove local sources of irritation: sharp edges on teeth are smoothed, the fit of a denture is checked, and any parts of orthodontic wires that dig in are covered. Depending on your symptoms, the dentist may arrange a protective product that covers the sore, an antiseptic mouthwash or a topical medicine they consider appropriate. Using these products on your own decision and for a long time is not recommended.
If recurrences are frequent, if the sores are large or long-lasting, or if fever and feeling generally unwell come with them, the assessment moves beyond the mouth. In that case blood tests and, where needed, referral to the relevant specialist come into it. A single sore that has not healed in two to three weeks is no longer accepted as an aphthous ulcer and needs to be investigated separately.
- The sore has not healed in two to three weeks
- The ulcers come with fever, tiredness and difficulty swallowing
- There are sores in the genital area, red eyes or joint pain along with the mouth sores
- The sore keeps coming back in exactly the same place, or its base has hardened
How is it prevented?
- Keep a short note of when the recurrences increase; this is usually how a trigger is found.
- Have sharp edges on teeth and poorly fitting dentures that make you bite your cheek put right.
- You can try a toothpaste without sodium lauryl sulfate for a while and see whether it makes a difference.
- Do not put aspirin, salt or caustic substances on the sore; these can make the sore bigger.
Frequently asked questions
- How can a mouth ulcer be told apart from a cold sore?
- Where it sits is the most practical distinguishing point. An aphthous ulcer appears on soft areas such as the inside of the cheek and lip, the edge of the tongue and under the tongue. A cold sore usually starts on the outer edge of the lip, gives a tingling first, then forms small fluid-filled blisters and crusts over. A cold sore is contagious; a mouth ulcer is not.
- Are mouth ulcers contagious?
- Mouth ulcers do not pass from person to person. They are not passed on by kissing, by sharing cutlery or by any other contact. When they are seen often in the same family, that comes from a shared predisposition, not from spreading. Where a sore could be confused with an infectious condition, the distinction needs to be made at an examination.
- Can I stop mouth ulcers from appearing altogether?
- No method is known that removes the recurrences completely. What can help make them less frequent is removing sources of irritation, noticing your triggers and having any deficiencies assessed by a doctor. Keeping your expectations within that frame is more realistic.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.