Why do we sneeze? We usually sneeze in order to remove an irritant from the nose.
There are many different things that make people sneeze, but the most common cause is when there is an irritant in the nose. This could be smoke particles, it could be dust, it could be anything. The nose is the body’s first line of defense against things that are trying to get inside and it is programmed to stop them.
We all have (whether we like to admit it or not) hairs inside our nostrils. Their job is to catch dirt and particles that have entered into the nose. Sometimes, particles can get through those hairs and reach the inner lining of the nose. When they come into contact with the lining, the lining starts to release histamines, which are used to communicate with the immune system. When the histamines are produced, they start a signal that is sent to the brain. The brain receives the signal, decides that a sneeze is in order and sends the command down the trigeminal nerve network. This is the 5th cranial nerve and it is responsible for sensation in the face and actions like biting and chewing.
The signal is received and the body gets ready to sneeze. The windpipe, back of the mouth, and nasal cavities are opened. At the same time, the soft palate and tonsils at the back of the mouth are depressed, while the tongue is raised to touch the roof of the mouth. The chest muscles are commanded to compress and a large volume of air is pushed out in a very short space of time. This air shoots up the windpipe and into the mouth. The air is prevented from going up the nose, which causes an area of low pressure at the back of the nose. This area of low pressure sucks air in through the front of the nose and it gets pulled down the back of the nose and into the mouth. The air flying through the nose picks up the contaminants and mucus as it goes and they are all forced into the mouth before being blown out with all of the air. This is why you should always cover your mouth when you sneeze. You are expelling air from your lungs along with saliva from your mouth and copious amounts of mucus. If you happen to have a cold, the viruses will be ejected along with all the mucus, spreading the disease.
Pepper often makes people sneeze for exactly the same reason. Pepper contains something called piperine, which is an irritant. It will get through the nose hairs and reach the lining of the nose, stimulating a sneeze. Some people also sneeze when they come into direct sunlight. This is called a photic sneeze and it affects about 25% of people. Nobody actually knows the reason why this happens, although there are some theories. It could be because some nerves are crossed and one stimulus can cause different nerves to trigger. It could be because some people are more sensitive to light and the brain misinterprets this signal. There could be another reason.
Some people also sneeze after they take snuff, although that isn’t the purpose of snuff. Snuff is made from finely ground tobacco leaves and it was very popular in Europe in the 18th century. It originally came, along with all forms of tobacco, from south America. It came into Europe through Spain and by the 18th century, it was everywhere. Often people who take snuff sneeze, but this is not the intent. The sneezing is caused in the same process as any other sneeze because the ground tobacco irritates the inner lining of the nose. Many snuff takers say that only beginners sneeze. The tobacco is the point of the snuff and when you inhale it you get a shot of nicotine, plus the scent of the tobacco. When it is taken in through the nose, it can reach the blood vessels very quickly and the impact of the nicotine is very fast. This is the reason why people snort cocaine as well. It can enter the blood through the nasal membrane and it can reach the brain without having to go through the stomach and liver first. The hit is stronger and faster. However, snorting snuff and cocaine can also make you sneeze. And this is what I learned today.
Photo by cottonbro studio: https://www.pexels.com/photo/a-sick-man-covering-his-mouth-4114713/
Sources
https://www.loc.gov/everyday-mysteries/food-and-nutrition/item/why-does-pepper-make-you-sneeze/
https://www.healthline.com/health/why-do-we-sneeze#when-we-sneeze
https://en.wikipedia.org/wiki/Sneeze
https://en.wikipedia.org/wiki/Photic_sneeze_reflex
https://en.wikipedia.org/wiki/Snuff_(tobacco)