text: what makes someone throw up? like what happens in your stomach and such to cause such a  thing?  i know too much alcohol or bad food but what does your stomach actually do to say something isn't good here vomiting occurs when the abdominal muscles and diaphragm contract vigorously while the stomach is relaxed. this reflex action is triggered by the "vomiting center" in the brain after it has been stimulated by:   nerves from the stomach and intestine when the gastrointestinal tract is either irritated or swollen by an infection or blockage   chemicals in the blood (drugs, for example)   psychological stimuli from disturbing sights or smells   stimuli from the middle ear