Coughing up bubbles is clinically known as coughing up foamy sputum, which can be seen for a variety of reasons, such as upper respiratory tract infections, chronic bronchitis, acute left heart failure and so on. 1. If there is an upper respiratory tract infection, the infection stimulates the respiratory tract to promote gas mixed with sputum, cough foamy sputum, sometimes accompanied by nasal congestion, runny nose. 2. If there is chronic bronchitis, the bronchial wall mucosal cell proliferation is obvious, causing cough, cough foam sputum or mucus sputum, sometimes often accompanied by wheezing. 3. If there is acute left heart failure, it may cause acute pulmonary edema, increased lung volume, cough, cough foamy sputum, often pink, sometimes accompanied by chest tightness, dyspnea and so on. Cough cough foamy sputum may also be other causes, such as pulmonary candida infection, alveolar carcinoma, bronchiectasis, etc. It is recommended to consult a regular hospital to clarify the cause of the disease and timely diagnosis and treatment.