An anal fissure is a tear in the lining of the lower rectum that causes pain duringbowel movements. The crack in the skin exposes the muscle tissue underneath, causing severe pain and bleeding during and after bowel movements. An anal fissure can affect people of all ages, but it’s most often seen in infants and young children straining during bowel movements or chronic constipation or diarrhea. An anal fissure usually is not a serious condition. 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.