To help identify the cause of your anal itch, the doctor may ask you to describe your current diet and medications, your bowel habits, and the way you routinely clean your anal area after a bowel movement. The doctor will review your medical history, including any history of rectal problems (hemorrhoids, fissures or fistulas) or skin problems (psoriasis, eczema or seborrhea). Your doctor's questions will be followed by a physical examination of your anal area and sometimes, by a digital rectal examination. If you have a history of skin symptoms involving other parts of your body, your doctor will want to examine these skin areas as well.
If your anal itch is due to a local irritation in the anal area, the doctor usually can diagnose the problem based on your history, diet and personal hygiene routine, and the results of your physical examination. Sometimes, the doctor will request a stool sample if he or she suspects a worm or parasite infection. Rarely, your doctor may need to examine the area by inserting a special viewing instrument called an anoscope into your anus. This can help your doctor determine whether the itch is being caused by a problem inside your rectum.