Canker sores can appear in the mouth and usually look white or gray and have a red border. They can appear by themselves or in small clusters but are not contagious. The exact cause of canker sores is still unknown, but most experts agree that bacteria, viruses and the immune system are involved. In addition, there is evidence to believe these types of sores appear during stressful times in our lives.
Canker sores usually resolve within a few weeks and over-the-counter mouthwashes and topical anesthetics can provide some relief. While the sores are healing it is a good idea to avoid spicy, hot or acidic foods as these may irritate the sores.