text: 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: \n\nNerves from the stomach and intestine when the gastrointestinal tract is either irritated or swollen by an infection or blockage \n\nChemicals in the blood (drugs, for example) \n\nPsychological stimuli from disturbing sights or smells \n\nStimuli from the middle ear