Bleeding from tooth brushing is a common phenomenon that occurs at any age and is usually caused by periodontal disease, cavities in the neck of the teeth, calculus irritation, and systemic diseases. 1. Periodontal disease: If the tissues around the teeth are diseased, it will easily lead to capillary expansion and congestion, gum edema and pain. Once the organism is not brushing properly or chewing harder food, it will make the gums appear bleeding symptoms. 2.Caries cavity in the neck of teeth: When there is caries cavity in the neck of teeth, but it is not filled in time, it is easy to stimulate the gum and lead to inflammation of gum, which will break and bleed seriously. When this symptom appears, it is recommended to deal with the local lesion in time and take anti-inflammatory medicine. 3, calculus stimulation: If there are a lot of bacteria in the neck of the teeth, it will stimulate the gums, making the gums appear red, inflamed, painful, and will bleed in serious cases. 4, systemic diseases: If the patient suffers from liver cirrhosis, hemophilia, elderly hypertensive disease, blood disease, etc., it is easy to bleed when brushing teeth. This symptom should be promptly seen by a hospital. Therefore, bleeding during normal tooth brushing may be due to the above-mentioned causes. It is recommended to go to the hospital for further examination according to its severity to clarify the cause and treat it symptomatically.