Aspirin is a widely used nonsteroidal anti-inflammatory drug (NSAID) that is commonly taken for pain relief, fever reduction, and anti-inflammatory purposes. However, long-term use of aspirin can cause stomach ulcers.

Aspirin works by inhibiting the production of prostaglandins, which are chemicals that cause inflammation and pain. While this is helpful for relieving pain and inflammation, prostaglandins also play a protective role in the stomach lining. They stimulate the production of mucus and bicarbonate, which help to protect the stomach lining from the acidic environment of the stomach.

When aspirin inhibits the production of prostaglandins, the stomach lining becomes more vulnerable to damage from the acid in the stomach. This can lead to the development of stomach ulcers.

According to a clinical trial [3], taking aspirin with food can help reduce the risk of stomach ulcers. The study found that taking aspirin with a meal decreased the risk of stomach ulcers by 50% compared to taking aspirin on an empty stomach. This is because food helps to neutralize stomach acid and reduce its harmful effects on the stomach lining.

In conclusion, aspirin causes stomach ulcers by inhibiting the production of prostaglandins, which protect the stomach lining from acid damage. Taking aspirin with food can help reduce the risk of stomach ulcers.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ASPIRIN
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970722/
[3] https://clinicaltrials.gov/ct2/show/NCT00594867