An important sign of mouth pain is a change in eating behavior. A dog with a tender mouth eats slowly and selectively, dropping food that is particularly coarse and large. A dog with pain on one side of the mouth often tilts her head and chews on the opposite side. With an extremely painful mouth, the dog stops eating altogether.
Excessive drooling is common in all painful mouth diseases. It is often accompanied by bad breath. Any form of halitosis is abnormal. Periodontal disease and gingivitis are the most common causes of halitosis in dogs.
Sudden gagging, choking, drooling, and difficulty swallowing suggest a foreign object in the mouth or throat.
Difficulty opening and closing the mouth is characteristic of head and neck abscesses, nerve damage, or jaw injuries.