People who are sensitive to tree pollen usually have symptoms in late March and early April. Grasses affect people in mid-May to late June. Mold spores that grow on dead leaves and release spores into the air are also common allergens. Depending on the allergen, the risk for an allergy attack is highest at different times of the day. Allergens in the house, such as house dust mites and pet dander, can cause year-long allergic rhinitis, called perennial rhinitis.
Molds growing on wallpaper, house plants, carpeting, and upholstery are also perennial allergens.
Nonallergic Rhinitis Nonallergic Rhinitis with Accompanying Immune Response. Some cases of chronic rhinitis are associated with increased numbers of white blood cells called eosinophils, which are components of the immune system. This form of rhinitis, however, does not depend on the presence of IgE and is not due to an allergic reaction. As with allergic rhinitis, nonallergic rhinitis can be triggered by cigarette smoke and dozens of other air pollutants. Other triggers include strong odors, alcoholic beverages, and exposure to cold.