There are two conditions that are considered as abnormal gag reflex issues. One is an absence and another is a hyperactivity of gag reflexes. An absence of gag reflex is marked with the subject feeling no impulse to throw up even when an object goes past the soft palate. The reason behind this is the absence of pharyngeal sensation due to defects in the nerves or neural signal transmission mechanism. Most common absent gag reflex causes are damaged glossopharyngeal or vagus nerves, brain death, or any other damage to the nerves or neural transmitters involved in the gag reflex induction process.

Hyperactive gag reflex is characterized by high sensitivity levels in the pharyngeal nerves and surrounding area of certain individuals which leads to evocation of gag reflex at the slightest instance. This overactivity of the gag reflex is generally experienced by infants who are often not able to swallow their food properly and tend to throw up much of it. Overactive gag reflex causes in adults, though rare, may include sensitivity to certain foods, reactions to some sort of medication, indulging in activities that involve high-intensity movements such as swimming, running, etc.