Sneezing is defined as making a sudden, violent, spasmodic, audible expiration of breath through the nose and mouth, especially as a reflex act. (Georgeson 2015). They can be triggered by smells, after exercise, in sunshine, and many more stimuli. The goal of this brief summary is to first investigate the scientific reason behind sneezing and then to analyze the impact of holding sneezes in.
Sneezing is a natural response, used by the body as part of the immune system. The action clears the nose of bacteria and viruses. The trigger causes a signal to be sent to the brain through nerves. This pathway can take different forms in different people, resulting in various triggers for people. When a sneeze trigger, and neural impulses are received by the brain, signals are sent to close the throat, eyes and mouth. This is followed by vigorous contracting of the chest muscles and then the throat quickly relaxes. This results in air, with saliva, mucus, and bacteria, being expelled from the mouth and nose. (Hatfield 2010) It is believed that sneezing acts as a natural reset for the nose. (Georgeson 2015)
To Hold or Not to Hold
The real question addressed by this summary is the question of holding back a sneeze or not. To note, this is not a question of whether or to cover ones nose/mouth while sneezing. Sneezes expel mucus and bacteria 5+ feet, so it is simple curtesy for the person sneezing to cover their nose/mouth (although not with one’s hand, which propagates the spread of germs).
Sneezes can exit the nose at speeds up to 100mph (44.7m/s). The sound of sneezes differ for different people, depending on the shape and size of their nose and the amount of air in their lungs at the time of the sneeze. (Orenstein 2015) This means the force of the sneeze could vary person-to-person, but for the purposes of this analysis, general uniformity will be assumed. The mass of the sneeze can be generally estimated by the volume in an average person’s lungs and the density of what is being expelled. This means that mass=(density)*(volume)=1.2 (kg/m^3)*500 (cm^3)=0.6g. Say a sneeze takes 0.5s (this can range quite a bit). The force produced by the sneeze is F=velocity*mass/time= 0.6*44.7/0.5=53.64gm/s^2.
This is the same force a big marble would exert when being dropped (experiencing the force of gravity). While this is not generally a dangerous amount of force, not letting this sneeze out will result in the force dissipating throughout the body. Again, this is not typically dangerous, but can, in rare cases, result in weakened blood vessels, issues with the diaphragm, ear drum injury, or damage to blood vessels in the eyes. These rare complications are usually flukes and are often related to other issues, but doctors do recommend that a sneeze in progress not be unnaturally stopped (this is different than stifling the urge to sneeze). (Binns 2010) In conclusion, while the force of a sneeze is not generally dangerous, is can be safer to sneeze into an arm or a tissue rather than try to contain sneeze.
Federation of American Societies for Experimental Biology. 2012. Allergies? Your sneeze is a biological response to the nose’s ‘blue screen of death’. July. Accessed December 13, 2015. http://www.sciencedaily.com/releases/2012/07/120731103035.htm.
Georgeson, Pamela. 2015. Scientific American, Why do we sneeze? Accessed January 13, 2015. http://www.scientificamerican.com/article/why-do-we-sneeze/.
Hatfield, Heather. 2010. Sneezing: Myths, Causes, and Surpising Facts. January 11. Accessed December 12, 2015. http://www.webmd.com/allergies/features/11-surprising-sneezing-facts.
Orenstein, Beth. 2015. Why We Sneeze, and Other Fun Facts About Sneezing. Accessed December 13, 2015.