Heartburn is a burning feeling in the chest caused by stomach acid travelling up towards the throat. Common conditions that can cause heartburn include GERD (acid reflux disease), hiatal hernia, gastritis, ulcers, H. pylori infection, and excess stomach acid. It can also be triggered by lifestyle factors like spicy or oily foods, late-night eating, stress, caffeine, alcohol, smoking, and being overweight. Certain medicines (like painkillers) can also worsen heartburn. If heartburn persists or worsens, it is best to get checked so the right treatment can be started.