Why does motion sickness trigger vomiting?

Kidney energy: According to meridians theory kidney meridian is the one that influences ear area. Kidney energy when is normal energy flows up and down the spine. During disharmony this starts flowing sideways and causes disruption to stomach energy causing gaging and vomitting. Interestingly with pyelonephritis - kidney infection vomiting is the main symptom sometimes.

Vestibular system: Motion sickness is created by a disturbance to the vestibular system of the inner ear---when this is activated it will often trigger nausea and then vomiting. Antihistamines inhibit this response.