北京的飞行时期通常从4月初到5月下旬持续。 Si Yao Lina, who is studying the physician of the Department of Respiratory and Critical Care at the Shougang Hospital of Peking University, is stated in a Zhongxin health interview from the view of the sensitive mechanism, the willow catkins themselves are not strong allergens, above all because their physical allergic In humans, the mucosa is stimulated by adhesive substances, and a moving source of pollution. （性健康Zhao Fangyuan实习生Qu sijia） 负责编辑：[Song Yusheng]