Allergic rhinitis, intermittent or persistent, is caused by the deposition of allergens on the nasal mucosa, a process that is followed by a hypersensitivity reaction (type I allergy
1). The intermittent and persistent types differ in terms of duration of illness and causative allergens: in most parts of the world, the most common allergens for intermittent allergic rhinitis are grass, tree, and weed pollens, while the most common allergens for persistent allergic rhinitis are house dust mites and domestic animals. The condition is characterized by sneezing, rhinorrhea, obstruction of the nasal passages, lacrimation, and nasal, conjunctival, and pharyngeal itching.
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