Q: Dear Dr. Mao,
What causes an ulcer?
A: The highly concentrated acid produced by the stomach is quite capable of burning a hole through the tissue of the stomach and duodenum (part of the small intestine). That it usually does not do so is a tribute to the effectiveness of the methods that the body uses to protect itself. However, sometimes these protective mechanisms fail, and the ever-present acid begins to produce an ulcer.
It is now believed that ulcers are caused by the bacteria Helicobacter pylori. Apparently, this previously ignored organism has the capacity to infect the stomach and, by so doing, to weaken the stomach lining.