Itchy anus after 20 days of external hemorrhoid surgery may be caused by the wound not healing completely, or scar irritation. 1. The wound is not healed: if the patient does not pay attention to the care and diet after the operation, it may cause the wound to heal slowly, there is exudate, and when the feces passes through the wound it will stimulate the perianal area, resulting in continuous exudate and stimulation of the perianal area, causing itching. It is recommended to eat a light diet, pay attention to hygiene, and have regular checkups. 2. Scar irritation: If the patient’s wound heals after surgery, scar will be formed, and for people with scar in the anus, there will be fecal stimulation when they have bowel movement, causing itching. It is recommended that such patients should pay attention to hygiene, such as itching is serious, can be used under the guidance of the doctor hemorrhoid cream or anti-itching ointment, such as Ma Yinglong hemorrhoid cream, tretinoin cream, etc., to avoid blindly use their own medication.