Bleeding when brushing teeth may be caused by trauma to the gums, or it may be caused by periodontitis, gingivitis, blood disease and other diseases. 1. Gum trauma: usually the patient usually brushes his teeth too roughly or the gums are stimulated by hard objects, which will cause the gums to be scratched, which can be manifested as bleeding when brushing teeth all the time. 2. Periodontitis: It is usually considered to be related to calculus, plaque, traumatic bite, smoking, heredity, mental stress and other factors. Patients often appear red and swollen gums, soft texture, and can be accompanied by periodontal pockets overflowing pus, tooth loosening and bleeding, which can also be manifested as always bleeding when brushing teeth. Some patients may also have periodontal abscess, bad breath and other symptoms. 3. Gingivitis: usually due to localized plaque, and also associated with food impaction, poor restorations, misalignment and crowding. Patients often appear gingival color, shape, texture and so on will change, appear free gums and gingival papilla bright red or dark red, full of interspace, gingival papilla hypertrophy, treatment of tight and tough, and so on. At the same time, the patient can also be accompanied by increased gingival sulcus fluid, probing bleeding and other conditions, which can also be manifested as brushing teeth always bleeding. 4. Hematologic diseases: the cause of the disease is more, mostly related to chemical, physical, genetic, immune, nutritional and other factors. Patients often appear anemia, bleeding, lymph node enlargement and other symptoms, so some patients also brush their teeth, frequent bleeding gums. Some patients may also have fever. It is recommended that when patients have the phenomenon of bleeding when brushing their teeth, they should actively seek medical treatment to clarify the cause of the disease and then treat it reasonably.