http://www.oramd.com/recedinggums/4-recedinggumline.htm Causes for bleeding gums may be traced to neglected gums, teeth or mouth. Bleeding gums are a sign of an unhealthy mouth, as there is no natural cause for bleeding gums. Periodontal disease can be a cause for bleeding gums. Canker sores, receding gums, and other oral health problems may also be cause for bleeding gums.