Old Dogs Coughing What Does This Mean?

Cough is response of all animals against irritations in the throat, lungs and air passage. Cough in dogs can be due to following reasons.

1. Respiratory tract infections
2. TB
3. Heart diseases
4. Heartworm
5. Mouth and tooth/teeth infections
6. Internal parasites
7. Allergy to pollutants and smoke
8. Distemper

Differential diagnosis is needed to start proper treatment which is possible by visiting a vet, so, take your dog to vet.