A mouth ulcer is a painful round or oval sore that forms in the mouth. Mouth ulcers commonly occur on the gums or lips but can also be found on and around the tongue and on the roof of the mouth.
The lining of your mouth is incredibly sensitive and any break in its surface exposes the nerves that lie in and beneath it. Anything that touches them, whether it’s food, liquid or a toothbrush, causes pain which means it can be difficult to eat, drink and even talk.
Minor aphthous ulcers present as a painful open sore inside the mouth or upper throat characterised by a break in the mucus membrane. The cause of aphthous ulcers (or canker sores) is unknown, but they are not contagious.
Mouth ulcers can last for a week or more unless the damage continues happening, in which case they will not disappear until the cause - for example, a rough tooth - is treated.
The other common type is a major aphthous ulcer, which occurs when someone is feeling stressed. They often appear for the first time during puberty and they can run in families. These can take a couple of weeks to heal.
Other more serious causes of mouth ulcers include herpes infection, inflammatory bowel disease and immune disorders, but these are usually accompanied by other symptoms around the body. Sometimes a deficiency in iron, vitamin B12 or folate is the underlying cause, so if you get recurrent ulcers or ulcers that are not healing, you should consult your GP.