Crohn's disease is a chronic inflammatory bowel disorder which causes ulcerations in the gut and can make digesting food painful.
The disease usually affects the small intestine and one in every thousand people in the UK is afflicted with this miserable complaint.
But now scientists believe they have found the cause of Crohn's disease, and they think it could be treated with Viagra.
The team of researchers from University College London say they believe the cause is the opposite of what has been supposed and is triggered by a weak immune system, rather than an overactive one where cells are attacked by the body's own immune system.
Crohn's was previously thought to be an auto-immune disease and was treated with immuno-suppressant drugs.
But the researchers led by Anthony Segal and colleagues have discovered that people with Crohn's have a weak and unresponsive immune system which does not repair damage easily.
They say the flow of blood to damaged cells is substantially reduced, and a drug such as Viagra, best known for its effects on erectile dysfunction, could help the healing process as it stimulates blood flow.
Since it was identified in the 1920s there have been many theories as to the cause of Crohn's and it was often compared with tuberculosis, but attempts to find an infectious agent have failed.
The research team compared the immune system response of Crohn's patients and healthy individuals to minor injuries, such as skin abrasions and discovered a difference in the number of white blood cells called neutrophils produced by the body to heal the damage in the bowel and on the surface of the skin.
The healthy people in the study produced far more neutrophils than Crohn's sufferers, showing that the immune response in people with Crohn's is damaged.
The scientists tested the inflammatory response to bacteria in the patients' immune systems to bacteria such as might be in the gut and found that Crohn's patients are unable to destroy bacteria that penetrate the intestinal wall because of their weakened immune systems.
It was found that Viagra helped to correct the low blood flow in patients.
Segal and colleagues now hope to run a clinical trial to establish whether a drug such as Viagra can help guts ulcerated by Crohn's to heal.
Segal does say that patients who are on medication should not now suddenly switch.
The research is published in the current edition of the Lancet.