Certain bacteria and drugs can cause ulcers
We used to think that stress caused sores in your stomach that doesn’t heal. We now know that prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen (Motrin®, Advil®), or naproxen (Aleve®), can interfere with stomach mucus.
Ulcers result when stomach acid reaches the lining, and when they bleed they can cause pain and even be life-threatening.
A bacterium called Helicobacter pylori, or H. pylori, also can cause ulcers. An Australian doctor proved this by drinking the bacteria himself, and he and his colleague won a Nobel prize for the discovery.