Hay fever reflects an immunoglobulin (Ig) E–mediated, type I hypersensitivity response to an environmental antigen (allergen) in a genetically susceptible individual. In most cases, it’s induced by wind-borne pollens: in spring, by tree pollens (oak, elm, maple, alder, birch, cottonwood); in summer, by grass pollens (crabgrass, bluegrass, fescue, and ryegrass); and in fall, by weed pollens (ragweed). Occasionally, hay fever is induced by allergy to fungal spores.

With perennial allergic rhinitis, inhaled allergens provoke antigen responses that produce recurring symptoms year-round.

The major perennial allergens and irritants include dust mites, feather pillows, mold, cigarette smoke, upholstery, and animal dander. Seasonal pollen allergy may exacerbate symptoms of perennial rhinitis.

With seasonal allergic rhinitis, the key signs and symptoms are paroxysmal sneezing, profuse watery rhinorrhea, nasal obstruction or congestion, and pruritus of the nose and eyes, usually accompanied by pale, cyanotic, edematous nasal mucosa; red and edematous eyelids and conjunctivae; excessive lacrimation; and headache or sinus pain. Some patients also complain of itching in the throat and malaise.

With perennial allergic rhinitis, conjunctivitis and other extranasal effects are rare, but chronic nasal obstruction is common and often extends to eustachian tube obstruction, particularly in children.

With both types of allergic rhinitis, dark circles may appear under the patient’s eyes because of venous congestion in the maxillary sinuses. The severity of signs and symptoms may vary from season to season and from year to year.

Some patients may develop chronic complications, including sinusitis and nasal polyps.