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Wise et al.

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that physician-diagnosed AR during infancy is independently associated with a doubling of the risk of developing asthma at age 11 years. In children and adults, AR is a risk factor for asthma according to a 23-year follow-up of college students. 1776 These studies were confirmed by other studies. 458,1764,1777-1786 Some of these studies showed that rhinitis is a significant risk factor for adult-onset asthma in both atopic and nonatopic subjects. 1779,1780,1783 Therefore, rhinitis is a risk factor independent of allergy for developing asthma in both adults 1779,1780,1783 and children. 597 In adulthood, the development of asthma in patients with rhinitis is often independent of allergy, whereas in childhood, it is frequently associated with allergy, 597,1785 as almost all asthma in children is allergic. Asthma and AR also share common risk factors. Sensitization to allergens is probably the most important. Most inhaled allergens are associated with nasal 1787 and bronchial symptoms, but in epidemiologic studies, differences have been observed (eg, in pollen allergy). Some genetic polymorphisms are different in the case of AR and asthma. Other risk factors for asthma such as gender, obesity, viral infections in infancy, exposure to tobacco smoke (passive smoking or active smoking), diet, or stress are not found as common risk factors for AR. Outdoor or indoor air pollution is still a matter of debate as risk factor for AR or NAR. 101 In summary, AR and NAR are risk factors for developing asthma. • Aggregate Grade of Evidence: C (Level 2a: 2 studies; Level 3b: 11 studies; Table X.A.3). The 2015 AR clinical practice guideline from the AAO-HNS has highlighted the overlap of AR and asthma, specifically recommending that clinicians should assess for and document associated medical comorbid conditions including asthma. 761 The guidelines also review and consider the impact of comorbid asthma on treatment decisions for AR, though the action statements may not apply to AR with comorbid asthma. However, there is a body of evidence to suggest that AR therapies, including INCS, 1296,1788-1790 oral antihistamines, 1791,1792 LTRAs, 7,1793,1794 and AIT 1672,1788,1795,1796 may benefit both conditions. Some of the most promising results in altering the course of allergic inflammation common to AR and asthma have been seen with AIT. 1678,1797,1798 Given this increased understanding of the relationship between AR and asthma as similar inflammatory processes affecting the upper and lower airways, respectively, the importance of understanding the overlap of AR treatment with the treatment of asthma is increasingly evident. The studies reviewed in this section are limited to prospective randomized trials to minimize inherent biases and weaknesses of retrospective studies. 1794 Allergen avoidance is often advocated for allergy treatment, specifically for AR and allergic asthma. 7 Despite the intuitive acceptance of this and reasonable biological plausibility, the evidence for benefit of avoidance and environmental control measures in AR with associated asthma is limited. A Cochrane review examining randomized trials of subjects with asthma who underwent chemical or physical methods to reduce HDM allergen found no benefit with these methods. 1799 Single allergen avoidance or elimination plans such as removing or washing pets, mattress coverings, removing carpeting, and use of HEPA filters have shown

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X.A.4. Treatment of allergic rhinitis and its effect on asthma

Allergen avoidance.

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