One year old with a cough for 3 weeks, what to do?

Many conditions: There are many causes of cough, but one that lasts 3 weeks is considered prolonged. Usually cough caused by uncomplicated viral illnesses lasts 7-10 days. I would suggest an evaluation for wheezing, inflammation in the lung, a secondary infection, an ear/sinus/throat infection and other causes . Your physician may order testing such as a chest radiograph to determine the cause and to advise rx