What are mouth ulcers?

Ulcers are painful sores that appear inside the mouth which are often red or yellow. They shouldn’t be confused with cold sores, which appear on the outer lips and are caused by a virus and are contagious. 

 Mouth ulcers often recover on their own, if they persist for more than 3 weeks you must see your dentist. 

 Most common causes of mouth ulcers 

 Traumatic Ulcers 

Usually a single mouth ulcer is due to trauma- damage caused by biting the cheek or tongue, or by sharp teeth, brushing or ill fitting dentures. Once the cause of trauma is removed, the ulcer soon resolves. 

Recurrent aphthous Stomatitis 

When there is no traumatic cause, recurrent small mouth ulcers that keep coming back, is called ‘recurrent aphthous stomatitis’. True cause of these ulcers is not known.  

 Least common causes of mouth ulcers 


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


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