There are always many people who say they have a lot of phlegm in their lives. Phlegm is the mucus that is secreted by the mucous membrane of the respiratory tract below the nasal cavity, such as the lungs and bronchi, and is used to expel foreign substances from the body. Healthy people generally have a small amount of phlegm every day. However, if a person has a respiratory disease, a large amount of sputum is produced when infected by disease-causing microorganisms. There are many reasons for phlegm, and the following are common: 1. purulent phlegm Phlegm is sticky or thin, light green or yellow-green in color, brown when mixed with blood, and fishy odor is emitted at the same time. Spitting out this kind of sputum is mostly seen in patients suffering from lung abscess, purulent bronchial dilatation, or patients with abscess chest broken into the bronchus. The condition of such patients is usually more serious and they should go to the hospital as soon as possible to see a doctor. 2.Mucus sputum Mucus sputum is mostly grayish white or colorless and transparent, and this kind of sputum is mostly seen in patients suffering from bronchitis, or in the early stage of pneumonia, and in the stage of bronchial asthma attack. 3, bloody sputum sputum with blood, due to the amount of blood varies, the blood color is different, indicating that the lesion site is different. For example, bright red sputum is mostly seen in tuberculosis and bronchiectasis; rust-colored sputum is mostly seen in lobar pneumonia; rotten peach-like or rotten fish-belly-like sputum is mostly seen in pulmonary schistosomiasis; brown-red sputum is seen in amoebic lung abscess; and red-brown sticky jelly-like sputum is mostly seen in Klebsiella pneumoniae infection. Since Klebsiella pneumoniae is very virulent and easily resistant to various antibiotics, the clinical manifestations are very dangerous, and the treatment is relatively difficult and the prognosis is poor, so those who have this kind of sputum should go to the respiratory medicine department of the regular hospital for treatment as soon as possible. 4, foamy sputum Its sputum is thin and with foam. If its foam is pale white, this is mostly seen in chronic bronchitis; if the foam is pink in color, it is commonly seen in pulmonary edema.