In response to a question on healthshare.com.au

The commonest causes of stomach and duodenal ulcers are:

• A bacterium (bug) called Helicobacter pylori (H. pylori)
  
• Anti-inflammatory painkiller medications - eg. mobic/meloxicam, ketorolac/toradol, ibuprofen/brufen, naprosyn/naproxen, voltaren, aspirin and similar drugs.

Other contributors to ulcers include smoking, and some other medications (prednisolone, steroids; alendronate/fosamax). Rarely, ulcers can be due to stomach cancers, previous stomach surgery, hormone-producing tumours (Zollinger-Ellison syndrome) or other medical conditions.

The H. pylori bacterium is common, often causes no early symptoms, and usually is only discovered if someone has a gastroscopy (telescope examination of the stomach). It is usually treated with medications and a follow-up “breath test” to make sure it has been eradicated.

Ulcers related to medications usually occur after longer use, but occasionally can occur with very short treatment courses.