Fig. 2. Nasopharyngeal lavage analysis and histopathological features of nasal mucosa. The Nasopharyngeal lavage fluids were stained with H&E (×400). All AIT groups exhibited decreased eosinophil counts in the nasopharyngeal lavage 24 hours after the last intranasal challenge compared to PC group (A). The nasal mucosa was stained with H&E, PAS, and toluidine blue to identify eosinophils, goblet cells, and mast cells, respectively (×400). The number of eosinophils (B), goblet cells (C), and mast cells (D) in the nasal mucosa decreased in all AIT groups compared to that in PC group.

H&E, hematoxylin and eosin; AIT, allergen-specific immunotherapy; PC, positive control; PAS, periodic acid-Schiff; NC, negative control; Met(100), 100 mg/kg metformin intraperitoneal injection; Met(300), 300 mg/kg metformin intraperitoneal injection; SCIT, conventional subcutaneous immunotherapy with house dust mite; SCIT-Met(100), conventional subcutaneous immunotherapy combined with 100 mg/kg metformin intraperitoneal injection; SCIT-Met(300), conventional subcutaneous immunotherapy combined with 300 mg/kg metformin intraperitoneal injection.

^*P < 0.05; ^**P < 0.01; ^***P < 0.001; ^****P < 0.0001.