An anal fissure is a small cut or tear in the lining of the anus. The crack in the skin causes severe pain and some bright red bleeding during and after bowel movements. At times, the fissure can be deep enough to expose the muscle tissue underneath. In most cases, the tear heals on its own within four to six weeks. Certain treatments can promote healing and help relieve discomfort, including stool softeners and topical pain relievers. Or your doctor may need to look for other underlying disorders that can cause anal fissures.