Mouth ulcers, also called canker sores, aphthous stomata and recurrent aphthous stomatitis, mostly occur on the inner cheek, inner lip, tongue, soft palate, floor of the mouth, and sometimes the throat. They are usually about 3-5mm in diameter – though for those sufferring chronic mouth ulcers often significantly larger, and appear 2 or 3 at a time, or worse still there can be 10-20 or more.
They often seem start by themselves as a small bubble or blister (this stage is easy to not notice) which then becomes an open and ulcerated pit or crevass when the pain really starts. Alternatively they can be started by trauma to the lining of the mouth (e.g. by accidently biting onesself).
The worst thing about mouth ulcers is the pain that they cause, which is constant, excruciating and made worse by eating, drinking and talking. The picture of the homunculus that you may recall from schooldays shows how very sensitive the mouth and tongue are compared to most other parts of the body – which explains the amount of discomfort caused by something so small.
Severe ulcers cause sufferers to actively avoid eating, drinking, talking and kissing, which can be awkward socially. Speech is painful resulting in a loss of clarity or enunciation – and sometimes spitting, which doesn’t help. Sufferers often get worn down by the pain and become fatigued and depressed, and so I have been told, irritable too.
No specific single cause has yet been isolated, though it seems they are not generally caused by infectious agents such as viruses or bacteria and are therefore not considered contagious.