A biting pain in the upper half of the abdomen is a chief sign of excess acid production in the stomach. The cells that release acid for the digestion of food may produce more acid than they normally would, and the excess acid leads to irritation, notes Mayo Clinic
One term for the pain and discomfort connected to this type of irritation is nonulcer dyspepsia. In other words, the patient feels like he has an ulcer, based on the intestinal discomfort, but he does not. Other signs of excess acid production include nausea, bloating, gas or feeling full even though one has only eaten a small amount of food, according to Mayo Clinic.
In addition to the excess production of stomach acid, it is possible for patients to have multiple conditions going at once. Some people develop an acid sensitivity, in which the tissues running inside the duodenum and stomach have developed too much sensitivity to acid levels that are normal, so they are easy to irritate. Other people develop sensitivity to particular types of food or even ingredients. Some common targets are citrus fruits, spices and vegetables that contain relatively high acid levels. Even coffee serves as the triggering irritant for many people, as stated by Mayo Clinic.