Blunted perception of dyspnea may predispose patients to fatal asthma attacks. To examine whether this impaired perception of dyspnea in patients with acute asthma could be corrected by anti-asthma therapy, the medical records of 104 consecutive asthma patients who had been hospitalized as a result of asthma attacks were analyzed retrospectively. During the course of treatment with conventional asthma medications, the forced expiratory volume in 1s (FEV1) and the Borg scale-based dyspnea perception scores during breathing through an inspiratory muscle trainer were measured at least twice. The baseline Borg score measured just before discharge was significantly lower than from that measured initially, regardless of improvement in FEV1. In contrast, the Borg score at the highest resistance (HR; 3.12+/-0.26 vs. 5.03+/-0.53; P<0.01) and the HR-induced DeltaBorg score (1.68+/-0.20 vs. 4.47+/-0.54, P<0.001) were increased significantly in the Poor Perceivers (Borg score 5 at HR and HR-induced DeltaBorg score 3). Patient age (r=0.363, P<0.001), blood eosinophil counts (r=-0.285, P<0.01), and serum total IgE levels (r=-0.213, P<0.05), but not FEV1, were significantly related to the effect of the treatment on the HR-induced DeltaBorg scores. These findings suggest that anti-asthma treatments decrease dyspnea even without a concomitant improvement in lung function and correct the impaired perception of inspiratory resistive load in acute asthma, and that age and allergy influence the effect of treatment on impaired perception.