The sneeze reflex (also known as ptarmosis), is a condition of sudden, uncontrollable expellation of air through the nares in response to numerous stimuli.
Sneezing usually occurs in response to mechanical irritation in the nasal cavity, which results in an afferent signal propagating through the ophthalmic and maxillary branches of the trigeminal nerve, to the trigeminal nerve nuclei in the brain-stem, but may occur as a result of even as benign a stimulus as looking at bright lights, peri-ocular inflammation, swirling water, bubbles up the nose, or simply brushing a tentacle along ones cheek.
The signal is interpreted in the trigeminal nerve nuclei, and an efferent signal goes to different parts of the body, such as mucous glands and the diaphragm, thus producing the sneeze. Stimulation of the ophthalmic branch of the trigeminal nerve may enhance the irritability of the maxillary branch, resulting in an increased probability of sneezing. The parasympathetic nervous system has many neighboring fibers that respond to different stimuli. Sensory input could travel to the neurons in the cortex that interpret such signals, with neighboring neurons which are involved in sneezing, also activate due to the generalization, and this can lead to a sneeze in response to a stimulus other than nasal irritation.
It is a myth that your heart stops briefly when you sneeze . What does occur when you sneeze, is that the intra-thoracic pressure within our chests fluctuates, this pressure change alters blood flow, which changes the rhythm of your heartbeat, and although you may feel as though your heart “skips a beat”, it actually doesn’t. However, you do actually blink when you sneeze, this is an automatic reflex, likely protective from foreign bodies, and lubricates the eye, it is not to prevent your eyes from popping out of your head, that is a myth. Equally a myth is that the Devil is blown out of your nose, or that your soul will escape out your nose, when you sneeze. None the less, sneezing can convey aerosolized germs, so it is a good idea to cover one’s nose and mouth with a tissue when sneezing; and it is still polite to say “Gesundheit”, or “Bless You” when you sneeze.
Bottom Line : Sneezing generally does not present any particular risks to the individual, and while occasionally a sign of illness, is usually more of an annoyance than a risk of injury.