Canker Sore Overview. Canker sores, also known as aphthous ulcers, are among the most common causes of painful sores in the mouth. 1  The classic lesion is a small (less than 1 centimeter) oval to round ulcer with a erythematous (red) border.2  They occur on the mucous membranes inside the mouth.anker Sore Overview. Canker sores, also known as aphthous ulcers, are among the most common causes of painful sores in the mouth. 1  The classic lesion is a small (less than 1 centimeter) oval to round ulcer with a erythematous (red) border.
Other Causes of Heavy Panting in Dogs. Heavy breathing or deep, intense panting can also be a symptom of eclampsia, also called milk fever. Eclampsia is a dangerous condition that affects nursing mothers; low blood calcium levels lead to an inability to stand or walk and tremors.
Once this disease gets severe enough to cause noticeable symptoms that are very clear to see, a Boxer dog may have: Fainting â When blood is not pumped correctly, this can cause lapses where the dog is not receiving enough blood flow and the dog can faint.