Because of the chemical nature of impulse and the axon-dendrite structure. Because of the chemical nature of impulse and the axon-dendrite structure. http://www.biologymad.com/nervoussystem/nerveimpulses.htm (Best technical explanation and excellent graphics and animations)
Newborns may sneeze, and this is typically attributed to the irritation of their nasal passages. The most common irritants, explains Dr. Iannelli, are smoke (and simply smoking outside is not enough), animal dander from pets in the house, dust mites, and mold.
Some people believed that a sneeze causes the soul to escape the body through the nose. Saying bless you would stop the devil from claiming the person's freed soul. Others believed the opposite: that evil spirits use the sneeze as an opportunity to enter a person's body. There was also the misconception that the heart momentarily stops during a sneeze (it doesn't), and that saying bless you was a way of welcoming the person back to life. We now know that sneezing is a reflex action and is most often the sign of something relatively benign, such as a cold or allergy.