Fast Cooling Relief of:. Heartburn and Acid Indigestion. Alka-Seltzer® Heartburn Relief extinguishes the fire of your worst heartburn. Its aspirin-free effervescent formula starts to work the instant you take it. . For effective relief of acid indigestion and upset stomach with headache or body aches and pains try Original Alka-Seltzer also available in great tasting lemon-lime. . And to break up your worst cold symptoms try Alka-Seltzer Plus® Cold.