Dry heaving occurs when you smell a nauseating odor, which is a normal physiological reflex that many people experience. The taste of nausea will make people have an uncomfortable reaction, the formation of a stimulating signal will act on the central nervous system, through the integration of the central nervous system for the sympathetic nervous system, parasympathetic nerves have a certain effect and stimulate the effect, easy to lead to the patient’s visceral receptors affected by the taste of nausea to produce a dry-heaving reaction. If the patient himself has some digestive diseases, such as chronic gastritis, gastrointestinal peristalsis is weakened and other conditions, through the taste or smell of stimulation is more likely to produce dry heaving reaction, and individual differences also have a certain relationship.