My advice to you is when kid having running nose or flu, cough and fever is best that you take them to pediatrician to check up 1st. As regard to feeding 八宝散 (I didnt buy YuYanSan), I feed my boy daily when he is about 2 mths only whether or not is sick. Not advicable to give when they are too young. 八宝散 is to help to build up his immunse is actually not meant for curing running nose or flu, cough and fever. I can recommand you to c this chinese doc she is very good & highly recommanded by friend & colleague.