Advil is a nonsteroidal anti-inflammatory drug (NSAID) that is commonly used to relieve pain and reduce inflammation. However, it can cause stomach problems in some people. According to the sources provided, Advil can cause gastrointestinal side effects such as stomach pain, nausea, vomiting, and indigestion [2][3]. Long-term use of Advil can also increase the risk of developing stomach ulcers, bleeding, and perforation [2].

To reduce the risk of stomach problems, it is recommended to take Advil with food or milk [2]. It is also important to follow the recommended dosage and not exceed the maximum daily dose [2][3]. People who have a history of stomach ulcers, bleeding, or other gastrointestinal problems should consult their doctor before taking Advil [2].

In conclusion, Advil can cause stomach problems in some people, especially with long-term use. To minimize the risk of gastrointestinal side effects, it is important to take Advil with food or milk, follow the recommended dosage, and consult a doctor if you have a history of stomach problems [2][3].

Sources:
[2] Hospital for Special Surgery. (n.d.). Guidelines to Reduce the Side Effects of NSAIDs. https://www.hss.edu/conditions_guidelines-reduce-side-effects-nsaids.asp
[3] GoodRx. (n.d.). Advil Side Effects. https://www.goodrx.com/advil/advil-side-effects