what can cause sores in mouth
Less commonly, mouth sores can be a sign of an illness, tumor, or reaction to a medication. Drugs that may cause mouth sores include aspirin, beta-blockers, chemotherapy medicines, penicillamine, sulfa drugs, and phenytoin.
Mouth sores may be caused by irritation from: 1  A sharp or broken tooth or poorly fitting dentures. 2  Biting your cheek, tongue, or lip. 3  Burning your mouth from hot food or drinks. 4  Braces. Chewing tobacco.