I have had a canker sore all week. I would have said I had a cold sore, but I just learned that canker sores and cold sores are not the same thing. Cold sores occur outside the mouth, canker sores inside the mouth. And canker sores are not contagious. So that's good to know; thinking I had a virus of the same family as genital herpes ravaging my body was unsettling. I was actually doing some stock research to avoid studying, and found out that a company I was considering manufactures a cold/canker sore product, which led me to this realization. The company, Closure Medical Corporation (CLSR), looks promising, but is a bit richly valued, so I intend to purchase their canker sore product and make my decision based on it's efficacy. Unfortunately, my cold sore is almost healed, but I should get an idea (and I'll have the product handy the next time a canker inflammation strikes).