HRH2 and asthma: injected histamine receptor (H1R and H2R) antagonists into the brain ventricles of stressed asthmatic mice and discovered a significant reduction in peripheral airway inflammation, and eosinophil and lymphocyte infiltrations were considerably lowered, which indicated that allergens under stress may increase the severity of the inflammatory response to asthma by stimulating the release of histamine to activate histamine receptors (H1R and H2R) in the brain region (49).