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.
Sneezing and many other allergy symptoms are caused by a histamine response in the body. A substance that triggers an inappropriate histamine response in the body is known as an allergen. Antihistamine medications may be used to reduce the occurrence of seasonal allergy symptoms. Histamine may cause contact dermatitis, a skin allergy reaction to soaps, bubble bath, detergent and other chemicals.