Cold sores and fever blisters are one and the same—small skin blisters on the mouth caused by Herpes simplex virus. When the virus acts up, the lips may become tender and blisters follow. Within a few days, blisters drain and dry, and the virus retreats to the nerve.
Treatments of choice: Acyclovir for serious outbreaks, zinc gluconate, even Blistex.
Canker sores are probably caused by a reaction to certain bacteria. Unlike cold sores, they occur inside the mouth and heal without medication in one or two weeks. Avoid coffee, spices, tomatoes, walnuts.
Treatments to ease pain: Cankaid, Orabase, Zilactin. And it couldn’t hurt to keep your fingers crossed.