How does histamine affect the body'?

Histamine is a chemical involved in immune responses, regulating physiological functions in the stomach, and acting as a neurotransmitter. It is released during allergic reactions, leading to symptoms like itching, swelling, and inflammation. In the stomach, histamine stimulates the secretion of gastric acid, aiding digestion. Additionally, it plays a role in the central nervous system, influencing sleep-wake cycles and appetite.