It may be unsightly and painful to have canker sores. This is why it makes more sense to prevent them from occurring rather than waste time finding a cure. Canker sore causes is still yet to be known, and it believed to be from a variety of factors : stress, acidic foods, low immune system, and poor oral hygiene. Since the real cause it yet to be defined, there is no cure for it yet. Fortunately, canker sores heal within a week or two. Additionally, there are many over-the-counter canker sore medications and remedies which can be used to help ease the pain and speed up the healing time.