Legionella May Drive Severe Symptoms in Seasonal Allergic Rhinitis in Children

Credit: Adobe Stock/ Volodymyr

A study found the reasoning behind why children with seasonal allergic rhinitis experience more severe symptoms than children with perennial allergic rhinitis.¹ Legionella, more prevalent in seasonal allergic rhinitis, may raise histamine via the FcεRI signaling pathway, protein digestion, neuroactive ligand-receptor interaction, synaptic vesicle circulation, and gastric acid secretion metabolic pathways.

Research has shown seasonal allergic rhinitis symptoms are worse than those with perennial allergic rhinitis. Seasonal allergies, which can be caused by tree pollen in the spring, grass and weed pollen in the summer, and ragweed in the fall, can vary in symptom intensity based on the type of weather.²

For instance, symptoms may be worse on hot, dry days when the wind blows the pollen; rainy days can be more bearable as the pollen is more likely to stay on the ground. People can take several measures to prevent seasonal allergic rhinitis, such as keeping windows closed, wearing glasses outside to protect their eyes, and showering before bed to wash off allergens from hair and skin.

As for perennial allergic rhinitis which can be caused by mold or animal dander, measures to prevent symptoms include washing hands after petting animals and using dust-and mite-proof bedding and mattress covers.

Investigators wanted to understand why seasonal allergic rhinitis symptoms were more severe, so they conducted retrospective microbiomics and metabolomic research to explore the nasal bacteria and metabolites in children with seasonal allergic rhinitis.¹ The findings of this study were presented at the 2025 American Academy of Allergy, Asthma, & Immunology (AAAAI) annual meeting in San Diego from February 28 – March 3.

“This is the first multi-omics study of nasal secretions from a pediatric AR population,” wrote their team, led by Wenjing Liu, from the department of otolaryngology, head and neck surgery at the National Center for Children's Health in Beijing, in their AAAAI late-breaker.

The sample included 174 school-age children with allergic rhinitis from August 2024 – June 2024. Children were categorized as having seasonal (n = 104) or perennial (n = 70) allergic rhinitis based on allergen detection results. The team collected data on nasal secretions and analyzed microbiomics and metabolomics based on the Illumina novaseq6000 sequencing platform.

As with previous research, this study also demonstrated that seasonal allergic rhinitis led to more severe symptoms and a greater quality of life impact in children than perennial allergic rhinitis. A microbiome analysis showed a greater abundance of Legionella and Neisseria in seasonal allergic rhinitis nasal secretions.

The analysis identified 139 metabolite differences between seasonal and perennial allergic rhinitis groups. Mantel tests showed Legionella upregulates histamine (P < .05). The KEGG analysis further demonstrated that the histamine is raised via FcεRI signaling pathway, protein digestion and absorption, neuroactive ligand-receptor interaction, synaptic vesicle circulation, and gastric acid secretion pathways.

“…different microorganisms and metabolites may be used as biomarkers and possible therapeutic targets for children with seasonal [allergic rhinitis],” investigators concluded.

References

1. Lui, W, Han, Y, Wang, P, et al. Candidate biomarkers suggestive of differences in seasonal allergic rhinitis in children: multi-omics analysis. Journal of Allergy and Clinical Immunology, Volume 155, Issue 2, AB458

2. Allergic Rhinitis (Allergies). https://familydoctor.org/condition/allergic-rhinitis/#:~:text=What%20causes%20allergic%20rhinitis?,are%20often%20due%20to%20ragweed. Accessed February 26, 2025.