The causes of blood around the anus are complex, such as external injury, constipation, anal fissure, hemorrhoids, dermatitis, tumors and so on, all of which can appear the symptoms of blood around the anus. 1. External injury: such as anal sex, or by the underwear friction, resulting in mucous membrane damage to the skin near the anus, triggering bleeding. 2. Constipation: its main symptoms include localized pain, difficulty in defecation, dry stools and so on. Some patients are too hard during defecation, which can damage the anal skin and mucous membrane, and then there are symptoms of blood around the anus. 3. Anal fissure: anal skin tears, the formation of ulcers, clinical manifestations of anal pain, bleeding, constipation and other symptoms. 4. Hemorrhoids: its main symptoms are anal bleeding, swelling, defecation difficulties, etc., which can also lead to the symptoms of blood around the anus. 5. Dermatitis: dermatitis caused by local skin infection can lead to congestion, redness and swelling of the affected area, and even cause bleeding. 6. Tumor disease: such as anal papilloma, hemangioma, etc., can also trigger this bleeding symptom. The cause of blood near anus is more complex, patients are advised to consult doctors to confirm the diagnosis in time and follow the doctor’s instructions to be treated accordingly.