Patients bleeding in the mouth, to find out what part of the bleeding, the causes include digestive system problems, acute periodontitis, malignant tumors, etc., as follows: 1, digestive system problems: patients mainly have problems with the digestive system, resulting in bleeding from the gastric mucosa, this situation will lead to blood in the mouth when coughing, spitting. If this is the case, it is recommended to visit the hospital to identify the cause and see if it is a problem of the digestive system. 2, acute periodontitis: If bleeding in the mouth, it is usually caused by acute periodontitis, which may cause red, swollen, painful and bleeding gums due to local stimulation of plaque, calculus and food debris in the mouth, and the saliva will have blood in it. In this case, you should consult a hospital in time to carry out periodontal basic treatment, remove the local stimulus such as dental calculus in the mouth, and apply local medicine, generally about a week, the inflammation can gradually disappear. 3, malignant tumors: malignant tumors of oral mucosa, such as tongue cancer, gum cancer, buccal mucosa cancer, etc., there will be bleeding when the lesion is broken, it is recommended to check and treat in hospital in time.