Canker sores are essentially due to type 1 herpes simplex virus (HSV-1), but on rare occasions can be a result of HSV-2. Once it gains entry into your system, the herpes virus will remain dormant in nerve endings. Periods of stress will activate the virus, and that's when the canker sores pop up. Any type of stress can activate HSV, including emotional and physical stressors. Once you have any type of HSV, you have it for life. Anti-viral medications are only used for controlling the frequency of outbreaks. But because HSV-1 is such a benign infection, anti-virals are not prescribed for it an medications are aimed at alleviating the symptoms. You can pick up some over-the-counter ointments like "Kanka," which is a topical anesthetic (benzocaine). As mentioned by previous posters, keeping the sore clean (with warm salt water rinses) is a good idea. Otherwise, stay away from things that will irritate the sore (i.e. spicy food, acidic food like orange juice, etc.).