It contains sodium alginate, which is naturally derived. It is classed as an “alginate” which means that it forms a “protective layer” over the stomach contents which helps to prevent acid coming back up into the oesophagus (food pipe). As such, it isfast actingand has asoothing effect, lasting up to four hours. It is effective at treating the classic symptoms of heartburn (a burning pain in the chest and mild acid regurgitation).