Acid reflux happens when the valve between your stomach and food pipe becomes weak or relaxes too often, allowing acid to move upward. This can be triggered by heavy meals, spicy or oily food, caffeine, citrus fruits, chocolate, mint, alcohol, smoking, stress, or lying down soon after eating. Overeating, obesity, and conditions like hiatal hernia also make reflux more likely. Eating smaller meals, avoiding trigger foods, reducing stress, and not lying down after meals help prevent it.