Can a cold sore appear in the mouth?

Yes: The mouth and lips are the most common area for young children to develop cold sores.

Yes: The membranes inside the mouth are usually involved with the first or primary flare of a cold sore and can be quite extensive. Later cold sores generally localize on the skin outside. Other viruses (hand-foot-mouth), trauma, apthous ulcers, allergic reaactions can all cause mouth sores on the inside.