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Wise et al.

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limited evidence-based clinical benefit for reducing asthma and/or AR symptoms. 101,1799,1800 However, there is theoretical benefit of reducing allergen exposure, a paucity of data on multimodality approaches to reduce allergen load, and minimal negatives to attempting these various techniques; therefore, allergen avoidance could be considered as part of a multifactorial approach in the management of asthma associated with comorbid AR. 1801,1802 (See section IX.A. Management – Allergen avoidance for additional information on this topic.) Pharmacotherapy: oral H 1 antihistamines.— We identified 6 RCTs which specifically evaluated oral H 1 antihistamines for the treatment of asthma in the context of coexistent AR (Table X.A.4-1). There are many oral H 1 antihistamine medications, but cetirizine and loratadine are the 2 most highly studied second-generation antihistamines used concomitantly in AR and asthma. There is biologic plausibility for a role of antihistamines in the treatment of allergic asthma, as elevated histamine levels after allergen challenge are associated with bronchoconstriction responses in acute asthma episodes. Cetirizine also has bronchodilatory effects which are significant both as monotherapy as well as in combination with albuterol. 1803 Despite improvement in asthma symptoms, objective measures using pulmonary function testing and peak expiratory flow have failed to demonstrate significant improvements. 1804-1806 Alternatively, there is growing evidence that antihistamines may have a preventive effect on the development of asthma in atopic patients, as shown in the Early Treatment of the Atopic Child trial. 1807 Briefly, atopic infants were treated with 18 months of cetirizine and followed for the development of asthma. While analysis of the entire group found no significant difference between cetirizine-treated and placebo-treated patients, subgroup analysis revealed approximately 50% reduced risk of developing asthma among certizine-treated patients with grass pollen and HDM sensitivities. The authors hypothesize that variation in key genes related to histamine regulation may explain these differences. 1807,1808 (See section IX.B.1.a. Management – Pharmacotherapy – Antihistamines – Oral H 1 antihistamines for additional information on this topic.) Pharmacotherapy: oral corticosteroids.— Oral corticosteroids are an effective component of the asthma treatment algorithm, particularly for cases which are inadequately controlled with bronchodilators and inhaled corticosteroids. 1809 They are also effective for symptoms of rhinitis. 1247 However, oral corticosteroids have significant side effects, especially with increasing duration of use. 7 Because of the side effect profile associated with these medications, they are not recommended for the routine treatment of AR, and utilization is only recommended for select cases after thorough discussion of the associated risks and benefits. (See section IX.B.2.a. Management - Pharmacotherapy - Corticosteroids - Oral corticosteroids for additional information on this topic.) Pharmacotherapy: intranasal corticosteroids.— In the 1980s, topical INCSs were reported to improve asthma symptoms in patients with coexistent AR and asthma. 1364,1810 Since then, it has been shown that very little intranasally administered corticosteroid reaches the lung (approximately 2%), suggesting this effect on the lower airway may be related to its intranasal effects. 1788,1811 We have identified 2 meta-analyses and 12 RCTs that address this potential “unified airway” effect of INCS on asthma (Table X.A.4-2). A 2003 Cochrane

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Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.