The most common problems associated with acidity are heartburn and acid reflux. Heartburn is that uncomfortable burning sensation in the center of the chest, especially after eating a large meal. Acid reflux occurs when you taste regurgitated food or a sour, bitter liquid in the back of your mouth or throat. Acidity symptoms can be very unpleasant and occur at the most inconvenient times, but, in general, they can be treated quickly and simply with drugs or natural products.