Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the symptoms of Cough ?
    ### Response:
    When you cough, mucus (a slimy substance) may come up. Coughing helps clear the mucus in your airways from a cold, bronchitis, or other condition. Rarely, people cough up blood. If this happens, you should call your doctor right away.
                
A cough may be a symptom of a medical condition.
    