Ulcers are sores that are slow to heal or keep returning. They can appear anywhere on your body, inside or outside. Common types include leg ulcers, peptic ulcers, bedsores, genital ulcers, corneal ulcers, and mouth ulcers. Causes vary: leg ulcers often result from poor blood flow; peptic ulcers are caused by excess stomach acid or infections; bedsores come from prolonged pressure on the skin; genital ulcers are usually from sexually transmitted diseases; corneal ulcers are due to infections or dry-eye syndrome; mouth ulcers can be triggered by various conditions like celiac disease or Crohn’s disease. Complications can be severe if untreated, such as infections or even blindness in the case of corneal ulcers.