Alka-Seltzer tablets are used for the temporary relief of various symptoms caused by too much stomach acid, such as heartburn, acid indigestion, and upset stomach. They work as an antacid that lowers the amount of acid in the stomach. Alka-Seltzer tablets are effervescent, meaning they dissolve quickly in water and contain three active ingredients: aspirin, sodium bicarbonate, and citric acid. Aspirin is a pain reliever and anti-inflammatory, sodium bicarbonate is an antacid that neutralizes stomach acid, and citric acid reacts with the sodium bicarbonate and water to form effervescence or a fizzy effect. Alka-Seltzer tablets are sold in foil packets, each containing two tablets. They are generally safe for most people, but there are some situations where they should not be used, such as if you are allergic to aspirin or have certain medical conditions. It is important to read the label and check the ingredients before using Alka-Seltzer tablets to ensure that you are using the correct product for your symptoms.