A2. A canker sore is another term for a mouth ulcer. People sometimes confuse canker sores with cold sores but there are noticeable differences between the two.
Cold sores are highly contagious sores which are caused by the herpes virus. They appear as a series of blisters on the outside of the lips and can be transmitted by kissing or other forms of personal contact.
Canker sores are not contagious and develop inside the mouth. They can be found on the tongue, inside the cheeks, inside the lips or on the roof of the mouth. In some cases they can develop inside the throat.