Gaviscon Dual Action Liquid is for the fast, soothing and long-lasting relief of heartburn and indigestion. This formula works in two ways. It reduces excess stomach acid to relieve discomfort and it forms a protective layer over the stomach contents to soothe the buring pain in your chest. Gaviscon Dual Action Liquid is for the fast, soothing and long-lasting relief of heartburn and indigestion. This formula works in two ways: It reduces excess stomach acid to relieve discomfort and it forms a protective layer over the stomach contents to soothe the buring pain in your chest.