Indoor Allergen Exposure Worsens Respiratory Infections in Children With Asthma

Research published in the Journal of Allergy and Clinical Immunology demonstrates that children with asthma who are exposed to high levels of indoor allergens are at an increased risk of developing upper respiratory viral infections with symptoms. Additionally, the investigators also observed that children were more likely to be sensitized to cockroach and mouse allergens rather than dog and cat allergens.^1,2

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For this study, data were gathered from the Environmental Control as Add-on Therapy for Childhood Asthma study. Allergen concentrations were measured in the air (eg, mouse) and settled dust (eg, mouse, cockroach, dog, and cat), and upper respiratory infections were determined by testing nasal mucus for viruses. Additionally, the investigators evaluated any associations between allergen concentrations and outcomes associated with upper respiratory infections, while accounting for age, sex, study month, season, health insurance, and household size.²

A total of 90 participants with asthma and a total of 192 observations were included. Of these patients, the majority were Black (92%) and had public insurance (92%). Approximately 27% (n = 52) of observations were positive for upper respiratory infections, and a doubling in cockroach allergen concentration increased the odds of infections with cold symptoms by about 18% (odds ratio [OR] = 1.18; 95% confidence interval [CI], 0.99-1.40). The odds of an upper respiratory infection with cold symptoms and pulmonary eosinophilic inflammation were also increased by 31% (OR = 1.31, 95% CI, 1.10-1.57), and the odds of an infection with cold symptoms and reduced lung function increased by 45% (OR = 1.45, 95% CI, 1.13-1.85).²

Overall, mouse allergen concentrations were positively associated with all outcomes. Associations were shown to be stronger among children who were sensitized to pest allergens.^1,2

“This research highlights the critical role that environmental factors, particularly those found in disadvantaged communities, play in exacerbating respiratory infections among children with asthma,” Darlene Bhavnani, PhD, infectious disease epidemiologist and assistant professor of population health at Dell Medical School at University of Texas in Austin, Texas, said in a news release. “By understanding these links, we can better target interventions to reduce exposure to harmful allergens and improve health outcomes in at-risk populations.”¹

A similar study also published in the Journal of Allergy and Clinical Immunology enrolled children with asthma who lived in urban areas to assess whether nasal allergen challenge (NAC) responses to cockroach allergens would improve after 1 year of subcutaneous immunotherapy (SCIT). Changes in nasal transcriptomic responses during NAC, skin prick test wheal size, serum allergen-specific antibody production, and T-cell responses to cockroach allergen were all assessed.³

Patients were randomly given SCIT with the cockroach allergens or placebo. These findings found that NAC Total Nasal Symptom Score (TNSS) did not differ between SCIT-assigned patients (n = 28) compared with placebo-assigned participants (n = 29). The authors observed that nasal transcriptomic responses correlated with TNSS, but a treatment effect was not observed. Cockroach serum-specific immunoglobulin E levels had decreased in similar trend in both groups, but decreased cockroach skin prick test wheal size was greater among those who received SCIT. T-cell interleukin (IL)-4 responses following cockroach allergen stimulation had decreased to a greater extent among SCIT compared with placebo, but no effect was observed for IL-10 or IFN-γ.³

“These results could help explain why some children, especially those who live in underserved areas, have more trouble with their asthma than others,” said Bhavnani in the news release.¹

REFERENCES

1. University of Texas at Austin. Indoor allergens worsen respiratory infections in children with asthma, study finds. News release. September 12, 2024. Accessed September 27, 2024. https://www.eurekalert.org/news-releases/1057814

2. Bhavnani D, Lilley T, Rathouz PJ, et al. Indoor allergen exposure and its association to upper respiratory infections and pulmonary outcomes among children with asthma. J Allergy Clin Immunol. 2024. doi:10.1016/j.jaci.2024.08.006

3. Zoratti E, Wood R, Pomés A, et al. A pediatric randomized, controlled trial of German cockroach subcutaneous immunotherapy. J Allergy Clin Immunol. 2024;154(3):735-744.e10. doi:10.1016/j.jaci.2024.04.022