The main symptom of GERD in adults is frequent heartburn, also called acid indigestion—burning-type pain in the lower part of the mid-chest, behind the breast bone, and in the mid-abdomen. Most children under 12 years with GERD, and some adults, have GERD without heartburn. Instead, they may experience a dry cough, asthma symptoms, or trouble swallowing.

The reason some people develop GERD is still unclear. However, research shows that in people with GERD, the ring-like muscles relaxes while the rest of the esophagus is working. A hiatal hernia may also contribute to GERD. A hiatal hernia happens when the upper part of the stomach and the ring-like muscle move above the diaphragm, the muscle wall that separates the stomach from the chest. Normally, the diaphragm helps the ring-like muscle keep acid from rising up into the esophagus. When a hiatal hernia is present, acid reflux can occur more easily. A hiatal hernia can occur in people of any age and is most often a normal finding in otherwise healthy people over age 50. Most of the time, a hiatal hernia produces no symptoms.

Other factors that may contribute to GERD include obesity, pregnancy, and smoking.
Common foods that can worsen reflux symptoms include citrus fruits, chocolate, caffeine and alcohol drinks, fatty and fried foods, garlic and onions, mint, spicy foods, and foods made with tomatoes or tomato sauce.