Rhona: Could you please tell me what causes mouth ulcers.

Harry: Well there are many, many causes. The commonest situation is that we don't know the cause. Your mouth ulcers occur recurrently - is that what you're saying? Rhona: Yes.

Harry: They occur every few weeks and they're very painful.

Rhona: Yes.

Harry: It's that type of recurrence of mouth ulcers for which we really do not know the cause. There are many theories that have been suggested - they say it may be stress, it may be germs, it may be certain types of allergy and so on. But the bottom line is that we really do not understand the cause and all we can do is treat it symptomatically. We may give mouth washes, we may sometimes give cortisone pellets, antibiotics and what have you. But the fundamental underlying cause is not known. Having said that, that applies to the common type of recurrent mouth ulcer. But there are many other causes of mouth ulcers, for example a badly fitting denture. There are also viral and bacterial causes, and if the ulcer persists one must always think of cancer. But that's a chronic ulcer and is usually associated with smoking, excessive drinking or both. But in your particular case I'm sure you've got the common recurrent mouth ulcers, which are called aphthous ulcers. And for that we don't know the cause, but fortunately you will live till 150 years with it, although I'm sure it's uncomfortable. From time to time you can treat it symptomatically, but that's really all you can do.