A physiologic reflex to rid of any irritants in throat or lungs. Occasional cough is normal or physiologic, persistent cough or productive cough or blood cough is pathological and needs a medical work up. Possible causes include but not limited to bronchitis, Flu, Pneumonia, Sinus infection, allergy, asthma, acid reflux, Tuberculosis, Emphysema, whooping cough. Diagnosis is often made via chest x-ray, CT lung scan, Pulmonary function test. Treatment varies from simple antibiotics, to anti-histamine or inhalers to anti-acid medications.