mouth sores—which include canker sores are a minor irritation and last only a week or two. In some cases, however, they can indicate mouth cancer or an infection, such as herpes simplex virus. Herpes simplex causes cold sores, or fever blisters, and is highly contagious.
Blister, likewise called aphthous ulcers, are little, shallow sores that create on the delicate tissues in your mouth or at the base of your gums. Not at all like mouth blisters, ulcer don't happen on the surface of your lips and they aren't infectious. They can be agonizing, be that as it may, and can make eating and talking troublesome.