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Characterized by sneezing; rhinorrhea; obstruction of the nasal passages; conjunctival, nasal, and pharyngeal itching; and lacrimation, all occurring in a temporal relationship to allergen exposure. Prevalence in North America is ~20% with a peak prevalence ~40% occurring in childhood and adolescence. Perennial allergic rhinitis occurs in response to allergens that are present throughout the year such as house dust (containing dust mite antigens) and animal danders.