Stomach or gastric contents contain acid necessary in the breaking up and digestion of food. Acid reflux washes these harsh contents and their chemicals up into the esophagus through the lower esophageal sphincter (LES). It is unknown why the LES sometimes does not close properly therefore allowing acids to rise up from the stomach cavity and damage the tissue lining the esophagus.

Research indicates that the LES of those with acid reflux, relaxes while the remainder of the esophagus is still working. Anatomical abnormalities such as a hiatal hernia may also contribute to the development of this condition. A hiatal hernia occurs when the upper part of the stomach and the LES move above the diaphragm, the muscle wall separating the stomach from the chest. Normally, the diaphragm helps the LES keep acid from rising up into the esophagus. However, when a hiatal hernia is present, acid reflux can occur more easily. This hernia can occur in people of any age although it is normal in healthy individuals over the age of 50.

Obesity, pregnancy and smoking all contribute to acid reflux. Additionally, frequently ingesting foods which cause acid reflux reactions and symptoms, can contribute to the continuation and permanence of the condition. Foods including citrus fruits, chocolate, caffeinated drinks and alcohol, fatty and fried foods, garlic and onions, mint flavoring, spicy foods and tomato based foods can bring about acid reflux reactions and should be avoided.