Allergic rhinitis is inflammation of the nasal passages caused by allergens. In patients with allergies, they can cause symptoms of congestion, sneezing, runny nose and post-nasal drip. Common allergens include grass, weed and tree pollen, dust mites, animal dander and saliva and mold spores. Patients may have seasonal allergies, also called “hay fever” or perennial allergies, which are all-year long.