Hydrogen inhalation: A novel approach to alleviating allergic rhinitis symptoms by modulating nasal flora

Allergic rhinitis (AR) is an allergic reaction dominated by the Th2 immune response in the nasal mucosa. The bacterial infection process affects the balance between Th1 and Th2 immune responses, and the level of exposure to environmental flora is closely related to the development of AR. Hydrogen (H₂) is a medical molecule with anti-inflammatory and antioxidant properties. This study aimed to explore the possible mechanism of action of H₂ on AR through its ability to regulate the balance of nasal flora.

Serum eosinophil count (EOS), immunoglobulin E (IgE) concentration, visual analog scale (VAS), total nasal symptom score (TNSS), and rhinoconjunctivitis quality of life questionnaire (RQLQ) were observed before and after hydrogen inhalation in AR patients. Skin prick test (SPT) was used to determine allergen sensitisation. Community composition and relative abundance of nasal flora were examined before and after hydrogen inhalation and in normal subjects using 16S rRNA gene sequencing.

There were no adverse reactions during and after hydrogen inhalation in AR patients, with a favorable safety profile and significant improvements in VAS, TNSS, EOS, and IgE (P < 0.05). Cavity flora 16S rRNA gene sequencing showed higher abundance of Ruminococcus and Erysipelotrichaceae flora in the nasal cavity of AR patients than in normal subjects, and their abundance could be down-regulated after H₂ inhalation. H₂ significantly increased the abundance of Blautia_faecis and negatively correlated with VAS, TNSS, EOS, and IgE.

H₂ may improve symptoms in AR patients by modulating the distribution of nasal flora. Trials with larger sample sizes are required to further test this hypothesis.

This trial was registered in the China Clinical Trial Registry (Registration No. ChiCTR2200062253).