Canker Sores are strictly intraoral meaning that canker sores occur only within the mouth. They are not contagious meaning they can not be spread from person to person and are not caused by a virus.
Current theories on the causes of canker sores have focused on the immune system. This research suggests that canker sores may be caused by the body's own immune system attacking the cells lining the inside of the mouth. Trauma to the inside of the mouth can trigger an outbreak of canker sores. This trauma includes overzealous tooth brushing, biting your cheek or tongue, and scraping the inside of your mouth with hard or sharp foods (like hard pretzels). Stress is another factor capable of triggering canker sores. We advise those patients susceptible to canker sores to try to reduce the stress in their lives. In today's society this is often easier said than done. Its well worth the effort, however, since reducing stress has other health benefits as well.
Research suggests that reactions to certain food products may be responsible for many cases of canker sores. Among the foods that may cause canker sores in certain people are: nuts, peanut butter, sea food, wheat products, chocolate, and milk. Also implicated as a factor for canker sore occurrence are deficiencies in certain vitamins and minerals - principally B12, iron, and folic acid. Several British studies have shown deficiencies in these levels of vitamins / minerals in a significant number of canker sore sufferers. U.S. studies, however, do not show the same correlation between levels of these vitamins / minerals and canker sore occurrences. One of the most exciting advances has been the establishment of the link between canker sores and an ingredient common to almost all toothpastes. The additive SLS or sodium lauryl sulfate may be a culprit in canker sore formation.