A chemical burn of the oral mucosa occurs as a result of a noxious agent placed in direct contact with the mucosa either by the patient or a dentist. Mild lesions (less irritating agents and/or shorter duration of contact) usually present as an alteration in texture, while more severe lesions (more irritating agents and/or longer duration of contact) usually present with symptoms ranging from sensitivity and soreness to outright pain. Some chemicals used by patients include aspirin (placed next to an aching tooth) and OTC preparations that contain phenols, peroxides and sulfuric acid. Chemicals used by dentists in the course of routine dental treatment include methylmethacrylate, formaldehyde, formocresol, sodium hypochlorite and others used during root canal treatment. This generally occurs within minutes (if the agent is more caustic) to hours after exposures and heals within a few days.

Thermal burns are ulcers of the oral mucosa cause by contact of hot foods with the oral mucosa. The biggest culprits are hot cheese in pizza and hot coffee/tea. Microwaved food may also cause burns because the food may be hotter in the middle than on the surface.

Electrical burns in the oral cavity are usually of the arc type, where the saliva conducts an electric arc from the source to the mouth. Most cases occur in young children biting live wires at the end of extension cords.