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.
Mold causes cold or flu-like symptoms such as sneezing and coughing. Sneezing is a common allergic response of the human immune system when a person breathes in allergens like mold spores. Even if you don't have a mold allergy though, mold spores can still make you sneeze by irritating your nose and throat. Inhaled mold spores irritate the mucus membranes along the air passages. Some of the mold spores even lodge in the lungs and airways leading to chronic coughing and sneezing.