The following factors are common: 1. Environmental influences, when stimulated by hot or cold air or polluted air in the surrounding environment, irritating dry cough occurs, which disappears immediately after changing the environment. 2. Acute upper respiratory tract infections, most of which have a congested pharynx, cough without sputum is irritating, and the baby is in good spirits mostly due to viral infections. 3, lower respiratory tract infection, the most common bronchitis or bronchopneumonia, can be accompanied by fever, wheezing, breathing difficulties, but the cough is not necessarily serious, and poor mental state requires timely hospital consultation.