How to differentiate the cough due to infection vs the cough due to fluid in lungs ? Initially a doctor prescribed antibiotics and cough syrup to which the cough didn't respond. Then after severe episodes of coughing, another doctor prescribed lasix for which there was immediate response. So, basically is there a difference between the cough due to fluid in lungs and the one caused due to infection. This makes us self assure that the reason for cough is justified. Thanks for your response.