5.without smoking history. healty controls group: 1.17-70 years old. 2.without smoking hitory or stop smoking for more than 2 years. 3.without chronic cough. 4.without chronic respiratory diseases. 5.without chronic heart, liver, kidney,and autoimmune disease. 6.with normal chest x-rays. 7.with normal pulmonary ventilation function,and histamine challenge test showed negative result.