Environmental Exposures: Evolving Evidence for Their Roles in Adult Allergic Disorders

Kaoru Harada; Rachel L. Miller


Curr Opin Allergy Clin Immunol. 2022;22(1):24-28. 

In This Article

Intervention Studies

Controlled intervention studies for allergic diseases have met many challenges. The recent National Asthma Education and Prevention Program (NAEPP) Coordinating Committee Expert Panel guidelines on asthma management included a systematic review of indoor allergen mitigation strategies on asthma outcomes and reported a low certainty of evidence favoring allergic asthma treatment with mitigation strategies that targeted indoor allergens. A multicomponent mitigation strategy aimed at multiple allergens was recommended over single-component interventions such as high-efficiency particulate air (HEPA) vacuum cleaners, pest removal, and carpet removal. Pest management for asthmatic patients with cockroach and mice sensitivity was the only intervention that was recommended either as a single-component or part of a multicomponent strategy. There was insufficient evidence regarding pet removal as part of a multicomponent strategy.[23] Notably, the studies cited to make these recommendations were published several years ago, highlighting the need for more recent studies evaluating mitigation strategies on specific asthma outcomes.

The World Allergy Organization published an expert consensus on allergic rhinitis aggravated by air pollutants in 2020 that recommended ventilation either through modern heating, ventilation, and air conditioning systems with HEPA filter or periodically opening windows.[24] A randomized, double-blind, and placebo-controlled study in South Korea evaluated the effect of air purifiers placed in participants' bedroom and living room with HEPA filters on allergic rhinitis among adults with dust mite hypersensitivity. Both PM2.5 and PM10 and use of allergic rhinitis medications decreased in the homes with air purifiers. However, symptom and quality of life scores did not appear to improve.[25]

A randomized controlled study investigated the effects of higher altitudes on asthma by enrolling patients in a hospital rehabilitation program at either a high-altitude (3100 m) or low-altitude (760 m) center in Kyrgyzstan. Both groups spent 3 weeks at the center and participated in activities such as patient education, endurance training, and breathing exercises. When fractional exhaled nitric oxide (FeNO) was obtained before and at the end of the rehabilitation program, participants in the high-altitude group had a significant reduction in FeNO compared to those in the low-altitude group.[26]

Dietary probiotics have been studied as an intervention given their hypothesized effects on restoring homeostasis within the host microbiome. Zwicker et al. studied the effects of intranasal treatment with Escherichia coli A0 34/86 (E. coli O83) during sensitization and airway challenge with ovalbumin in mice. Treatment with E. coli O83 reduced airway hyperreactivity and airway levels of eosinophils and Th2 cytokines (IL-5, IL13), with additional experiments supporting a mechanistic role of toll like receptor 4 signaling.[27] The authors interpreted these findings to indicate that local administration of probiotic to mucosal airway surfaces may be an effective therapy for allergic airway inflammation.