hello user There are many reasons of haemoptysis !! It may be due to weak capillaries of the lungs causing it to bleed even on coughing. It might also be a old injury inside the bronchi caused by bronchoscopy, which bleeds spontaneously or due to cough. The other reason for haemoptysis are bronchitis and pneumonia most commonly, but also core pulmonale , lung neoplasm (in smokers, hemoptysis is often persistent), aspergilloma, tuberculosis, bronchiectasis, coccidioidomycosis, pulmonary embolism, pneumonic plague, and Cystic Fibrosis. hope my info helped you regards Dr Hari Om Chandrakar MBBS