Mouth Ulcers

Dental Health Advice

What causes mouth ulcers?

Dental Trauma

A single mouth ulcer can be due to trauma e.g. biting the cheek or tongue, sharp teeth, tooth brushing or poorly fitting dentures

Recurrent Aphthous Stomatitis (RAS)

A common problem and leads to repeated bouts of mouth ulcers in otherwise healthy children and young people. The cause is not known, but it is not infectious and is unlikely to be inherited – this means that they cannot be passed on from person to person.

Minor ulcers are the most common. They can appear inside the cheeks, on the lips, tongue and gums and, more rarely, on the roof of the mouth. Most of these ulcers are the size of the top of a pencil and can sometimes come in clusters. You can get four to six at any one time.

Large ulcers are more severe and can take longer to heal. Any ulcer that lasts longer than 3 weeks, should be checked out by your dentist. Large ulcers may appear near the tonsils and can be very painful, especially when swallowing. You usually only get one at a time.

It is also possible to have up to 100 very small painful ulcers which last for one to two weeks.

However, these last two varieties are very rare.

You may get ulcers in other parts of the body such as your eyes or genital area. It is important to tell your dentist about this.


Infections can cause mouth ulcers. Herpes simplex often leads to widespread mouth ulcers in children and some adults. Other less common viral and bacterial infections may cause mouth ulcers, but this is rare.


Cancer of the mouth can first appear as a mouth ulcer. The ulcers caused by mouth cancer are usually single and last a long time without any obvious local cause (for example a sharp tooth). Any ulcer that lasts longer than three weeks should be looked at by your dentist. Ulcers caused by cancer usually appear on or under the tongue, but may occasionally appear somewhere else in the mouth. Cancer of the mouth is usually associated with heavy smoking and drinking. Doing both together greatly increases the risk.

Other causes of mouth ulcers

Mouth ulcers can be caused by anaemia and occasionally by other blood disorders and some skin or gastrointestinal diseases. Sometimes the mouth ulcers are the only sign of an underlying disease.

How can The 247 Dentist help with dry mouth?

The treatment of mouth ulcers depends on the cause of the ulcers:

Traumatic ulcersRemoving the source of the irritation will eliminate the ulcer.
RASThese ulcers will spontaneously heal within 3 weeks and often do not recur at all after childhood. Treatment involves maximising comfort whilst they resolve.
InfectionUsually similar management to RAS but may require other treatment to eliminate the infection.
CancerUrgent referral along a cancer care-pathway.
OtherBlood tests and appropriate treatment of causative factors.  

If an ulcer lasts more than 3 weeks you should always ask a dentist for advice. The247dentist can help diagnose the cause of the ulcer or ulcers within your mouth and therefore enable appropriate action to be taken.

You may be able to reduce the risk of mouth ulcers by: Maintaining good oral hygiene and using high-quality toothbrushes (to reduce the risk of damage to your mouth).

Eating a good diet which is rich in vitamins A, C and E and which includes foods such as fresh fruit and vegetables (to lessen the risk of mouth cancer).

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