Stomach acid is important for normal digestion, but sometimes it can travel to the wrong place and cause pain and discomfort.
Heartburn occurs when stomach acid escapes into the oesophagus (which connects the throat to the stomach). As the oesophagus doesn’t have the same protective coating as the stomach, the acid can cause damage and inflammation, which can lead to a burning pain in the chest that can spread up towards the neck.
Reference: 1. Sigterman KE, et al. Cochrane Database of Systematic Reviews 2013, Issue 5. Art. No.: CD002095.