Canine Chronic Inflammatory Rhinitis  Rebecca C. Windsor , DVM ⁎ , , ,  Lynelle R. Johnson , DVM, PhD, DACVIM †  ⁎ Department of Clinical Sciences at North Carolina State University, Raleigh, NC.  † Diplomate of the American College of Veterinary Internal Medicine, Department of Medicine and Epidemiology at the University of California, Davis, CA.  http://dx.doi.org/10.1053/j.ctsap.2005.12.014 , How to Cite or Link Using DOI  Permissions & Reprints Chronic inflammatory rhinitis is commonly found in dogs with chronic nasal disease and is characterized by lymphoplasmacytic infiltrates in the nasal mucosa in the absence of an obvious etiologic process. The pathogenesis of lymphoplasmacytic rhinitis remains unknown. Animals respond poorly to antibiotics, oral glucocorticoids, and antihistamines, making primary infectious, immune-mediated, or allergic etiologies unlikely. Aberrant immune response to inhaled organisms or allergens may induce inflammation in some animals. Common clinical signs include nasal discharge, sneezing, coughing, epistaxis, and stertor. Diagnosis is made by performing a thorough history, physical examination, radiography or advanced imaging (via computed tomography or magnetic resonance imaging), rhinoscopy, and nasal mucosal biopsy to rule out primary etiologies of nasal discharge. Treatment strategies have included various antibiotics, antihistamines, oral and inhalant steroids, nonsteroidal antiinflammatories, and antifungal medications. Some dogs may respond partially to doxycycline or azithromycin, although it is unclear whether response is related to antimicrobial or antiinflammatory properties of these drugs. Hydration of the nasal cavity through nasal drops or aerosols may limit nasal discharge, and some animals may improve with inhalant (but rarely oral) glucocorticoids. Keywords  rhinitis;  nasal;  canine;  inflammatory;  lymphoplasmacytic The most common causes of chronic nasal discharge in dogs include nasal neoplasia, fungal rhinitis, and lymphoplasmacytic rhinitis (LPR), also referred to as inflammatory rhinitis. Other causes of chronic nasal disease include nasal foreign body, rhinitis secondary to dental disease, parasitic rhinitis (Pneumonyssoides caninum), and primary ciliary dyskinesia. Idiopathic LPR is recognized with increasing frequency in the canine population and may be more common in certain geographic locations. Diagnosis is made via histopathologic identification of a lymphoplasmacytic infiltrate in the nasal mucosa with exclusion of specific causes of chronic inflammation. An effective therapeutic regimen for dogs with LPR has not been established, largely because the underlying pathogenesis is still unknown. Etiology The etiology of LPR has not been determined, although infectious, allergic, and immune-mediated mechanisms have been suggested. LPR may have a multifactorial etiology in some dogs and/or different etiologies in different dogs, making it difficult to develop general treatment guidelines. Primary Infection Primary bacterial infection of the nasal cavity is rare, and no single infectious organism has been identified in dogs with LPR. However some dogs respond anecdotally to certain antibiotics including doxycycline and azithromycin, leading to the speculation that certain bacterial organisms such as Chlamydophila, Mycoplasma, or Bartonella could be involved in the pathogenesis of LPR.