Allergic Rhinitis - Allergic Rhinitis - Merck Manual Professional Edition

Allergic rhinitis is seasonal or perennial itching, sneezing, rhinorrhea, nasal congestion, and sometimes conjunctivitis, caused by exposure to pollens or other allergens. Diagnosis is by history and occasionally skin testing. First-line treatment is with a nasal corticosteroid (with or without an oral or a nasal antihistamine) or with an oral antihistamine plus an oral decongestant.(See also Overview of Allergic and Atopic Disorders.)Allergic rhinitis may occur seasonally or throughout the year (as a form of perennial rhinitis). Seasonal rhinitis is usually allergic. At least 25% of perennial rhinitis is nonallergic.Seasonal allergic rhinitis (hay fever) is most often caused by plant allergens, which vary by season and geographic location. Common plant allergens includeSpring: Tree pollens (eg, oak, elm, maple, alder, birch, juniper, olive)Summer: Grass pollens (eg, Bermuda, timothy, sweet vernal, orchard, Johnson) and weed pollens (eg, Russian thistle, English plantain)Fall: Other we...