Another reason for reverse movement of food in the stomach is gastritis. In such a case inside layer of the stomach becomes swollen. Very spicy food, food items causing allergy or side effects of aspirin can cause swelling inside the stomach. Swollen muscles are not able to pass the food towards small intestine so the food is moved in the reverse direction through reflux.
Result? Acidity! Burning sensation in the chest. And thereafter a dash for the chemist’s shop for antacid tablets, and then ‘instant relief‘! Antacid gives some relief but it does not remove the underlying cause of acidity.
Gastric acid (Wikipedia)