- A broken/fractured tooth
- Something stuck in the mouth/cheek/roof of the mouth
- Periodontal disease
- Nausea (illness possibly from a dietary indiscretion)
- Toxin exposure
- Recent seizure
- Nausea due to organ problems (kidney disease)
- A hypersensitivity reaction (i.e. bee sting)
To help settle the stomach you could try one of the following drugs. My favorite product is Pepcid (an over-the-counter antacid).
Pepcid comes in 10mg or 20mg tablets. You can give it every 12 hours.