Aspirin is a commonly used medication for pain relief, but it can cause stomach problems as a side effect. According to the NHS [2], some of the most common side effects of aspirin include stomach aches, indigestion, and nausea. These symptoms can be more severe in people who take high doses of aspirin or who take it for a long time. Additionally, aspirin can cause stomach ulcers and bleeding in some people, particularly those who are older or who have a history of stomach problems.

According to Health Harvard [3], aspirin works by inhibiting the production of prostaglandins, which are chemicals that cause inflammation and pain. Unfortunately, prostaglandins also play a role in protecting the stomach lining from damage caused by stomach acid. When aspirin reduces the production of prostaglandins, it can leave the stomach lining vulnerable to irritation and damage. This can lead to stomach problems such as ulcers and bleeding.

It is important to note that aspirin is not recommended for everyone, and that the risks and benefits of taking aspirin should be carefully considered before starting treatment. According to Drug Patent Watch [1], aspirin can interact with other medications and medical conditions, so it is important to talk to a healthcare provider before taking aspirin.

In conclusion, aspirin can cause stomach problems as a side effect, including stomach aches, indigestion, nausea, ulcers, and bleeding. These side effects can be more severe in people who take high doses of aspirin or who take it for a long time. It is important to talk to a healthcare provider before taking aspirin, especially if you have a history of stomach problems or are taking other medications.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ASPIRIN
[2] https://www.nhs.uk/medicines/aspirin-for-pain-relief/side-effects-of-aspirin-for-pain-relief/
[3] https://www.health.harvard.edu/heart-health/answers-about-aspirin