An antacid is a type of medication that helps neutralize stomach acid. It is commonly used to relieve symptoms of heartburn, indigestion, and upset stomach. Antacids work by increasing the pH level in the stomach, making it less acidic and providing quick relief from discomfort. These medications are available over-the-counter in various forms, including tablets, liquids, and chewables. Common active ingredients in antacids include calcium carbonate, magnesium hydroxide, and aluminum hydroxide. While effective for occasional use, it is important to consult a healthcare professional if symptoms persist.