Pain is worst before meals and at bedtime, when the stomach is usually empty. Both types are also called peptic ulcers. The stomach is the most acidic part of the body, setting the stage both for ulcer development and infection. The mucous-secreting cells also produce histamine, which stimulates the parietal cells to release acid. The stomach needs the acid environment for the digestive enzyme pepsin to break down proteins in foods.
Acidity is measured using the pH scale.
Many body fluids, including blood, tears, pancreatic juice, and bile, are in the 7 to 8 pH range. Gastric juice, in contrast, has a pH of 1.6 to 1.8. That's more acidic than lemon juice, cola drinks, and coffee. The environment in the small intestine is far less acidic than in the stomach, but because it receives the acidic mixture of semi-digested food from the stomach, it is prone to ulceration too. The stomach's innermost lining, the mucosa, protects it from digesting itself.