If the cold and cough is often bad, you need to go to the hospital for blood tests, lung CT, mycoplasma infection, blood culture and sputum culture to analyze what causes it, usually for the following reasons: First, the cold and cough is often bad may be the emergence of respiratory infections, from the upper respiratory tract to the lower respiratory tract, lung and deep pathogenic bacteria infection will appear cold and cough delay. Second, cold, cough often bad, there will also be the case of allergic or allergic asthma, the upper respiratory tract is prone to allergic season, contact with allergens will appear a certain allergic reaction, at this time will also appear cold, cough often bad. Third, if improper medication or medication errors, such as bacterial colds if the antiviral, viral colds taking antibacterial drugs, mycoplasma infections when not taking anti-mycoplasma drugs, this will also lead to colds and coughs are always bad.