A mouth ulcer is the loss or erosion of part of the delicate tissue that lines the inside of the mouth (mucous membrane). There are multiple causes. The most common cause is injury, such as accidentally biting the inside of your cheek. Other causes include aphthous ulceration, certain medications, skin rashes in the mouth, viral, bacterial and fungal infections, chemicals, some systemic medical diseases and, rarely, malignancy.

In most cases, mouth ulcers are harmless and resolve by themselves within 10 days without the need for any treatment. Aphthous ulcers are recurring ulcers with no known cause. They affect around 20 to 30 per cent of the population.

See your dentist if your mouth ulcers don’t clear up within a few days, or if you get them frequently.

Symptoms of mouth ulcers:

The symptoms of a mouth ulcer depend on the cause, but may include:

• one or more painful sores on part of the skin lining the mouth
• swollen skin around the sores
• problems with chewing or tooth brushing because of the tenderness
• irritation of the sores by salty, spicy or sour foods
• loss of appetite.

Aphthous ulcers generally occur on the softer mouth lining of the lips, cheeks, sides of the tongue, floor of the mouth and back of the palate and tonsil area. These ulcers are usually no larger than a 5 cent piece. You may develop more than one aphthous ulcer at a time, and sometimes these ulcers are continuous.

Causes of mouth ulcers:

Mouth ulcers can be caused by a wide range of factors including:

• accidental biting of the inside of your cheek
• injury from a toothbrush (such as slipping while brushing)
• constant rubbing against misaligned or sharp teeth
• constant rubbing against dentures or braces
• poor oral hygiene
• burns from eating hot food
• irritation from strong antiseptics, such as a mouthwash
• oral thrush infection
• viral infections such as the herpes simplex viral infection (cold sore)
• reaction to certain medications
• skin rashes in the mouth (for example, lichen planus)
• autoimmune diseases 
• underlying gastrointestinal disease such as Crohn’s disease
• oral cancer.

Investigation of mouth ulcers

If ulcers are interfering with your normal daily activities, see your dentist or an oral medicine specialist.

To find out the cause of mouth ulcers, careful examination is required. Your dentist or oral medicine specialist may order blood tests if they suspect you may have an underlying deficiency(such as an iron or vitamin B deficiency) or an inflammatory condition.

If your oral health professional cannot determine the cause of your mouth ulcers, or if the ulcers do not respond to the normal treatments, you may need to have a biopsy of part of the ulcer and some of the surrounding tissue. A biopsy is a procedure where a tissue sample is taken for examination and diagnosis.

Treatment for mouth ulcers:

Most mouth ulcers are harmless and resolve by themselves within 10 days. Other types of mouth ulcers, such as the aphthous variety or those caused by herpes simplex infection, need topical treatment such as a mouthwash, ointment or gel.

It isn’t possible to speed the recovery of ulcers, but the symptoms can be managed and the risk of complications reduced.

Treatment options for mouth ulcers include:

• Avoid spicy and sour foods until the ulcers heal.
• Drink plenty of fluids.
• Regularly rinse your mouth out with warm, slightly salted water.
• Keep your mouth clean.
• Take pain-relieving medication, such as paracetamol.
• Apply antiseptic gel to the ulcers.
• Use an alcohol-free medicated mouthwash containing chlorhexidine gluconate.
• Use a topical steroid mouthwash or ointment – generally prescribed by your dentist or oral medicine specialist.
• If required, use immunosuppressant medication as prescribed by your oral health professional. (This is required, rarely, for severe oral ulceration.)

Prevention of mouth ulcers:

Suggestions on how to reduce the likelihood of mouth ulcers include:

• Brush your teeth gently with a soft toothbrush, taking care not to slip with the brush.
• Eat a well-balanced and nutritious diet.
• Try to make sure that underlying medical conditions are well-controlled