The itching of the anus after a bowel movement has many causes and should be seen by a hospital in a timely manner, combined with a medical history and rectal examination to clarify its cause. 1, it may be fecal, such as fecal incontinence or anal sphincter relaxation, which can easily lead to fecal staining of the perianal skin, causing local irritation and itching. 2, if the diet is large amounts of stimulating food, such as chili peppers or after drinking a lot of alcohol, it will lead to anal discomfort, causing anal itching.