Most mouth sores are cold sores (also called fever blisters), canker sores, or a mechanical irritation caused by: - Biting your cheek, tongue, or lip
- Chewing tobacco
- Braces
- A sharp or broken tooth or poorly fitting dentures
- Burning your mouth from hot food or drinks
Cold sores are caused by herpes simplex virus and are very contagious. Usually, you have tenderness, tingling, or burning before the actual sore appears. Herpes sores begin as blisters and then crust over. The herpes virus can reside in your body for years, appearing as a mouth sore only when something provokes it. Such circumstances may include another illness, especially if there is a fever, stress, hormonal changes (like menstruation), and sun exposure. Canker sores are NOT contagious and can appear as a single pale or yellow ulcer with a red outer ring, or as a cluster of such lesions. The cause of canker sores is not entirely clear, but may be related to: - A virus
- A temporary weakness in your immune system (for example, from cold or flu)
- Hormonal changes
- Mechanical irritation
- Stress
- Low levels of vitamin B-12 or folate
For unknown reasons, women seem to get canker sores more often than men. This may be related to hormonal changes. Less commonly, mouth sores can be a sign of an underlying illness, tumor, or reaction to a medication. Such potential illnesses can be grouped into several broad categories: Drugs that might cause mouth sores include chemotherapeutic agents for cancer, aspirin, barbiturates (used for insomnia), gold (used for rheumatoid arthritis), penicillin, phenytoin (used for seizures), streptomycin, or sulfonamides.
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