Is a canker sore supposed to bleed?

It can: If it is very large, then bleeding may occur. There are many mouth ulcers called canker sores , so a professional diagnosis is important to rule out even cancer.

Some do: A canker sore disrupts the tissue down to the basement cell layer and minor trauma can often trigger breakage of a small capillary or more. Just keep the area clean and both will healin time.