Whether pneumonia is contagious or not is related to the cause of pneumonia. Pneumonia caused by different causes cannot be generalized and should be analyzed specifically. 1. Pneumonia refers to inflammation of the airway terminals, alveoli and interstitium, manifested by fever, cough, shortness of breath and other symptoms, which may be caused by pathogens, immune damage, allergies or medications, etc. Pneumonia may be caused by pathogens, immune damage, allergies or medications. 2. Pneumonia caused by pathogens such as viruses, mycoplasma, tuberculosis and other infections is contagious and can be transmitted through droplets. If the body resistance is weak at this time, it may cause lung inflammation. Can also be accompanied by respiration release part of the pathogen into the air, if the neighborhood and then inhaled into the body may have caused the infection. But different pathogens caused by pneumonia infectious size varies, generally speaking, Mycobacterium tuberculosis caused by the most infectious. 3. Radiation damage, foreign body inhalation, drug stimulation, physical and chemical factors, etc., may also cause patients to develop lung inflammation. Pneumonia caused by these factors is non-infectious, so it is generally not contagious. When patients find pneumonia, do not panic and worry, it is recommended to go to the hospital in time to receive timely examination and timely treatment under the guidance of the doctor.