Colds, also known as epiglottitis, or acute upper respiratory tract infections, are a common childhood illness. According to statistics, babies and young children catch as many as 4-6 colds per year, especially when they first start kindergarten. Most colds in babies are caused by viruses. After weaning, the antibodies inherited from the mother begin to weaken, while their own immune function has not yet been established, the amount of sIgA secreted by the respiratory tract is very small, which can not protect the mucous membrane of the respiratory tract from bacterial and viral invasion, coupled with the complex environment of the kindergarten, making babies susceptible to catching a cold.