To debunk this myth, let's first take a look at what's going on inside the body during a sneeze. Sneezing is a protective mechanism that the body uses to expel dust, pollen, pet hair and other allergens.
Some people sneeze when they're exposed to cold air. It's common to sneeze when you have a cold because the blood vessels inside of the nasal cavity become swollen and more sensitive than usual. This sensitivity triggers sneezing as soon as the nose detects irritating particles.
The act of sneezing considered an autonomic reflex, which is a fancy way of saying involuntary. When an irritant comes in contact with the nasal lining, the nerves in the area send a message to the lower portion of the brain, known as the medulla. The brain then triggers the activity necessary for the body to sneeze:
The muscles in the chest expand, the diaphragm contracts, and the lungs fill with air. The muscles that are in the back of the throat and vocal cords also contract, and then the stomach and chest muscles follow suit.
Finally, the sneeze is expelled through the mouth, sending between 2,000 and 5,000 droplets of mucus and air flying away from the body at between 70 and 100 miles per hour (112.6 and 160 kph) [source: Washington Post]. The spray from a sneeze can extend 5 feet (152.4 centimeters) from the sneezer [source: Library of Congress]. This spray is made up of saliva and mucus. Expelling the mixture through the mouth clears the nasal cavity.
One other thing happens during this process: Your eyes squeeze shut. But why? There's got to be some legitimate reason, right?