Normally a thick layer of alkaline mucus effectively protects the cells lining the stomach from the low pH of stomach acid. If this mucus becomes disrupted, however, acid comes into contact with the organ’s lining, damaging the cells and resulting in an ulcer.
Around 60 per cent of stomach ulcers are caused by inflammation due to chronic infection by the bacterium Helicobacter pylori. Bacterial by-products damage the cells lining the stomach, causing a breakdown of the top layers of tissue.
Non-steroidal anti-inflammatory drugs (NSAIDs), like ibuprofen and aspirin, also cause stomach ulcers in large doses. They disrupt the enzymes responsible for mucus production, diminishing the protective barrier.