What causes allergic rhinitis?

In allergic rhinitis, the immune system is hypersensitized to an allergen and responds with an overreaction to remove the allergen from the body. The body releases histamine and other chemical mediators that cause symptoms of allergic rhinitis (sneezing, runny nose, etc) in an attempt to neutralize and remove the offending substance.^[1] It should be noted that this reaction by the body to allergens is typically maladaptive, as the offending allergen is rarely dangerous.