actually, canker sores (which occur inside the mouth) are not related to the herpes simplex virus. their root cause is unknown, although there are a variety of possible contributing factors, including diet, physical trauma, and the use of toothpastes containing sodium lauryl sulfate (you can buy toothpastes for canker sore sufferers which are SLS-free).

cold sores, which occur on the lips, are the oral manifestation of herpes simplex.