How do antacids relieve stomach symptoms?

Antacid pros & cons. Many antacids work by neutralizing acid in your stomach. Some contain simethicone that helps break up gas bubbles in your stomach. One floats on top of acid so it "coats" as the acid is refluxed. In any case, antacids must be taken multiple times a day to keep acid neutralized, and benefits are short-lived. Magnesium-containing ones can promote diarrhea; calcium-containing ones can increase acid!