Bronchial Hypersensitivity in Asthmatics in Long-term Symptom-Free State

Improvement of asthmatic symptoms was shown to be closely associated with a decrease in bronchial hypersensitivity to histamine inhalation. Thus, the patients' clinical backgrounds were compared between 26 long-term cases whose symptom-free state lasted more than 1 year and 15 short-term cases whose symptom-free state ceased within 1 year. Among backgrounds, only the intrinsic type of asthma was significantly higher in number in the long-term group than in short-term group (65 percent vs 27 percent). The histamine threshold after the patients became symptom-free was significantly higher in the long-term group. In the short-term group, the values of PC20 just before the termination of the symptom-free state were all less than 5,000 mg/L of histamine. However, in the long-term group, the values of the PC20 for the final test were mostly over 5,000 mg/L. Decrease in bronchial hypersensitivity is considered to be a very important aim of therapy in bronchial asthma.