Mucus flowing from a dog's mouth is not necessarily canine distemper, but may also be caused by gastroenteritis, poisoning, stomatitis, gum inflammation, etc. It needs to be judged based on the actual situation of the dog. If the dog still has vomiting and diarrhea, is in low spirits, does not eat or drink, has blood in the stool, etc., it is best to take the dog to the pet hospital for examination and treatment immediately; if the dog has no abnormality, you can check whether the dog's oral cavity is healthy.