Rhinitis is the inflammation of the nose while sinusitis is the inflammation of the nasal passage. The term "rhinosinusitis" has been coined to include both conditions, as one rarely occurs without the other. Rhinitis and sinusitis can and does affect all breeds at any age, although long nosed breeds and young dogs are slightly more at risk.
There is a misconception among dog owners that both conditions are same and refer to "runny nose". The fact is there could be nothing further from the truth. Rhinitis is inflammation of the mucous membrane of the nose. Sinusitis is inflammation of the associated paranasal sinuses. The two conditions are far more potentially dangerous conditions than they appear. The rhinosinusitis can cause nose bleeds to occur, ocular discharge, as well as something very sinister in the dog; facial deformity. In fact, this condition can become so serious that if develops into a chronic condition; there is no known cure for it. Rhinosinusitis may be acute or chronic, noninfectious or infectious.
There are a variety of symptoms which can be seen in dogs affected by rhinitis and sinusitis, including:
Loss of appetite (anorexia)
Nasal discharge (i.e., mucus)
Decreased air flow (stuffy nose) in one or both nasal passages
Reverse sneezing (when the animal takes in a gasp of air to pull discharge in the back of their nasal passages down into their throats)