Experimental protocol.

<p>BALB/c mice were sensitized with 0.05% OVA and 2% aluminum hydroxide (Alum) solution by intraperitoneal injection on days 1, 8, and 15. Mice were challenged with a 4% OVA solution by daily intranasal instillation from day 22 to day 29. With sensitization and challenge, 2ME2, CoCl₂ or vehicle (DMSO) solution was given by intraperitoneal injection 2 hours before each intranasal challenge. SAL, saline; VEH, vehicle; IP, intraperitoneal injection; IN, intranasal instillation.