Summary

  • A mouth ulcer is the loss or erosion of the delicate lining tissue of the mouth (mucus membrane).
  • The most common cause is mechanical injury, such as accidentally biting your cheek.
  • In most cases, mouth ulcers are harmless and resolve by themselves in a few days without the need for medical treatment.
  • Aphthous ulcers are recurring ulcers with no known cause that affect around 20 per cent of the population.
  • If your mouth ulcers don’t clear up within a few days, or if you are troubled by frequent attacks, see your doctor.
A mouth ulcer is the loss or erosion of part of the delicate tissue that lines the inside of the mouth (mucous membrane). Some of the causes include certain drugs, chemicals and infectious diseases such as herpes or thrush. The most common cause is mechanical injury, such as accidentally biting your cheek.

In most cases, mouth ulcers are harmless and resolve by themselves in a few days without the need for medical treatment. Aphthous ulcers are recurring ulcers with no known cause that affect around 20 per cent of the population.

See your doctor if your mouth ulcers don’t clear up within a few days, or if you are troubled by frequent attacks.

Symptoms of mouth ulcers


The symptoms of a mouth ulcer depend on the cause, but may include:
  • A round sore or sores inside the mouth
  • Swollen skin around the sores
  • Tenderness
  • Problems with chewing or toothbrushing because of the tenderness
  • Irritation of the sores by salty, spicy or sour foods
  • Loss of appetite.

A range of causes


Mouth ulcers can be caused by a wide range of factors including:
  • Accidental biting of the 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
  • Herpes simplex viral infection (cold sore)
  • Reaction to certain drugs, such as chemotherapeutic agents
  • Autoimmune diseases (for example, lichen planus)
  • Syphilis infection
  • A range of other infections including hand-foot-mouth syndrome
  • Certain diseases including tuberculosis, AIDS, diabetes mellitus and inflammatory bowel disease
  • Cancer of the lip.

The cause of aphthous ulcers isn’t known


Around one in five adults suffer from recurring bouts of aphthous ulcers, which are mouth ulcers with no known cause. The tongue, gums or mouth lining can be affected. Crops of these tiny off-white ulcers tend to sprout during times of emotional stress or the menstrual period.

This has led some researchers to suggest that aphthous ulcers may be caused by an immune system reaction, since the immune system is affected by stress and hormones. The underlying trigger may be a virus or an allergic reaction. Another name for aphthous ulcer is canker sore.

Complications of mouth ulcers


Untreated, mouth ulcers can occasionally lead to complications, including:
  • Bacterial infection
  • Inflammation of the mouth (cellulitis)
  • Tooth abscess.

Diagnosis of mouth ulcers


It is important to establish the cause of the mouth ulcers. Some of the investigations may include:
  • Physical examination – mouth ulcers look different depending on their cause. For example, if the ulcer is large and yellow, it was most likely caused by trauma. Cold sores inside the mouth tend to be very numerous and spread around the gums, tongue, throat and inside of the cheeks. A fever also suggests the ulcers may be caused by a herpes simplex infection.
  • Blood tests – check for signs of infection.
  • Skin biopsy – a small tag of tissue from the ulcer is taken and examined in a laboratory.

Treatment for mouth ulcers


Most mouth ulcers are harmless and resolve by themselves in a few days. Other types of mouth ulcers, such as the aphthous variety or those caused by herpes simplex infection, need medical treatment. It isn’t possible to speed the recovery of ulcers, but the symptoms can be managed and the risk of complications reduced.

The range of treatment options includes:
  • 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-killing medication, such as paracetamol.
  • Apply antiseptic gel to the ulcers.
  • Use a medicated mouthwash.
  • Use steroid gels or tablets.
  • Treat aphthous ulcers with anti-inflammatory drugs.
  • Treat ulcers caused by the herpes simplex virus with anti-viral drugs.
  • Treat oral thrush with anti-fungal drugs.
  • Immunosuppressant drugs are sometimes required.

Prevention of mouth ulcers


Suggestions on how to reduce the likelihood of mouth ulcers include:
  • Brush your teeth at least twice every day.
  • Floss regularly.
  • Visit your dentist regularly.
  • Brush your teeth very gently, taking care not to slip with the brush.
  • Eat a well-balanced and nutritious diet.
  • Make sure that underlying conditions, such as diabetes mellitus and inflammatory bowel disease, are managed appropriately.

Where to get help

  • Your doctor
  • Dentist
  • Pharmacist

Things to remember

  • A mouth ulcer is the loss or erosion of the delicate lining tissue of the mouth (mucus membrane).
  • The most common cause is mechanical injury, such as accidentally biting your cheek.
  • In most cases, mouth ulcers are harmless and resolve by themselves in a few days without the need for medical treatment.
  • Aphthous ulcers are recurring ulcers with no known cause that affect around 20 per cent of the population.
  • If your mouth ulcers don’t clear up within a few days, or if you are troubled by frequent attacks, see your doctor.
References
  • Dental care - common conditions - 0 to 5 years, 2002, Better Health Channel, Department of Health, State Government of Victoria, Australia. More information here.
  • Aphthous ulcers, 2010, DermNet NZ. More information here.

More information

Mouth and teeth

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Last updated: August 2013

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