An anal fissure is a split or tear in the anal lining, often caused by a hard bowel movement, or by frequent loose stools. It causes pain, which can be very severe, and rectal bleeding. A swollen skin tag often develops on the outside of the anus when a fissure is present. Many acute fissures heal by themselves, but if they become chronic some form of treatment is needed. This typically involves topical ointment such as 2% nitroglycerine (Rectogesic) or 2% diltiazem. If the fissure fails to heal surgical therapy is often required.