Allergic rhinitis in a herd of cattle.

Allergic rhinitis was identified in a herd of Hereford cattle. Affected cattle had clinical signs of rhinitis (eg, nasal discharge, sneezing, nasal irritation, and nasal pruritus) and multiple small proliferative lesions in the nasal passages. Eosinophils were the predominant cell type in nasal discharges, and histologic examination of nasal mucosa biopsy specimens revealed chronic proliferative eosinophilic rhinitis. Results of CBC were normal; plasma fibrinogen concentrations were within reference limits. Results of intradermal allergen sensitivity testing and an ELISA for allergen-specific IgE only suggested an exaggerated IgE-mediated response to environmental allergens. Allergen-specific IgG may have acted as a competitive blocking antibody and limited clinical signs of disease in some cattle.