Pink frothy sputum is mostly caused by the infiltration of fluid from the capillary left vessels into the interstitial or alveolar lung. A common clinical case of pulmonary edema is acute heart failure. Because acute left heart failure causes increased pulmonary venous pressure, increased plasma exudation from alveolar capillaries, and even capillary rupture, acute pulmonary edema is formed, which is protein-containing fluid in the form of plasma or pink, and under the action of airflow, it forms foamy, just like increased urine protein content then has bubbles. It is often clinically differentiated from lobar pneumonia. Lobar pneumonia is an acute inflammatory disease caused primarily by Streptococcus pneumoniae, with lesions involving more than one lung segment and dominated by diffuse fibrinous exudation in the alveoli. The lesion begins in a localized alveolus and rapidly spreads to a lung segment or the entire lobe. The onset of the disease is rapid and often begins with high fever and chills, followed by chest pain, cough, rust-colored sputum, dyspnea, and signs of solid lung changes and increased peripheral blood leukocyte count. The course of the disease is about one week, the body temperature drops suddenly and the symptoms disappear. The disease mostly occurs in young and strong males. Common triggers of the disease include cold, exertion or rain. It belongs to the category of wind and temperature and pulmonary carbuncle in Chinese medicine. In contrast, pink foamy sputum is caused by fluid penetration from capillaries into the interstitium or alveoli of the lungs. The common clinical causes of pulmonary edema are cardiogenic pulmonary edema and nephrogenic pulmonary edema.