By Dr. Mercola
The tickle at the back of your nose lets you know that within seconds you’ll be sneezing. A sneeze is also called a sternutation. This explosive release of fluid and air from your lungs, mouth and nose is involuntary and many times your body’s response to irritants in your nasal cavity.
During a sneeze your soft palate comes down and the back of your tongue rises to close off your mouth, routing most of the air from your lungs through your nose. But, since you can only partially close of your mouth with the soft palate and tongue, a considerable amount of air and fluid will also exit through your mouth.
Scientists do not believe that you can sneeze during your sleep as your body experiences a nearly complete inhibition of motor neurons, and thus movement during rapid eye movement (REM) sleep.1 This lack of movement is called REM atonia. A complete REM cycle takes approximately 100 minutes,2 but you may awaken long enough to sneeze during an REM cycle or between them.
The volume of your sneeze may change over time. In some, the sneeze is loud and voluminous while others give a small toot. However loud or large, your body uses a sneeze to rid your nose of an irritant, germ or mucous and to clear the passage for better airflow.3 Pet dander, dust, pollen and germs are all common reasons to sneeze, but your body responds with a sneeze to other triggers as well.
Why Do You Sneeze?
If you suffer from seasonal allergies, you’ll likely have experienced the irritating and burning sensation in your nose that immediately precedes a sneeze. Those protein-based allergens are irritating and frustrating. Sneezing protects your body by clearing your nasal cavity of viruses and bacteria.4 Scientists know that more than allergens and germs trigger this sensation.
Dr. Neil Kao, allergy and asthma specialist from Greenville, South Carolina, explains that sneezing starts in your nervous system when signals passing along your nerves may take different paths to and from the brain.5 This can result in different ways in which people experience sneezing. For instance, you may have experienced a sneeze when plucking your eyebrows that triggered a nerve supplying your nasal passages, and thus you sneeze.
Exercise and sex are two surprising triggers for sneezing. Kao believes that during hyperventilation the mucous membranes in your mouth and nose begin to dry up. In response, your nose may begin to drip and trigger a sneeze.6 Sex stimulates the parasympathetic nervous system that may trigger signals during orgasm, resulting in sneezing.
It is not uncommon to sneeze more than once, or several times in succession. Dr. Marjorie Slankard, director of the allergy clinic at Columbia-New York Presbyterian Medical Center, believes the reason you may sneeze multiple times is related to the reason you started sneezing in the first place.7 In other words, sometimes it takes two, three or even four sneezes to rid your nasal cavity of what irritates it.
Researchers have found evidence that sneezing may be a natural way your nose and brain “reboot” in much the same way your computer reboots after Microsoft Windows’ infamous blue screen of death.8 Biochemical signals regulate the beating of microscopic ciliary hairs that line your nasal cavity triggering a sneeze and literally resetting the environment within your nasal cavity to near normal conditions.9
Data suggests that those who suffer chronic sinusitis may have limited ability to clear their nasal cavity despite the outward appearance of a “normal” sneeze. Researcher Dr. Noam Cohen, from the department of otorhinolaryngology head and neck surgery at the University of Pennsylvania, was involved in the study and commented on how a better understanding of effective sneezing may improve quality of life, saying:10
"While sinusitis rarely leads to death, it has a tremendous impact on quality of life, with the majority of symptoms coming from poor clearance of mucus. By understanding the process by which patients with sinusitis do not clear mucus from their nose and sinuses, we can try to develop new strategies to compensate for their poor mucus clearance and improve their quality of life."
Superstitions Are Something to Sneeze Over
There are many superstitions surrounding sneezing that have developed over years and many cultures. For instance, it is not true that your heart stops during a sneeze.11 Instead, your chest contracts and your blood flow may be constricted, changing the rhythm of your heartbeat, but the heart definitely doesn’t stop.
During a sneeze your eyes involuntarily close, giving rise to the superstition that your eyes will pop out of your head if your lids are not closed tightly during a sneeze.12 Despite the discomfort closing your eyes may elicit while driving, there is nothing you can do to keep your eyes open while sneezing, much like the involuntary reflex you have when the doctor taps the tendon under your knee cap.
Kao points out that while blood pressure in the eye may increase slightly during a sneeze, it is not nearly enough to cause the orb to pop out of your head.13 Other myths about sneezing include if your cat sneezes it’s going to rain, or when you sneeze either people are coming to visit your home or someone is thinking about you.14 Decades ago British nurses believed that babies were under a fairy spell until their first sneeze, and in Tonga, when a child sneezes it means bad fortune for the family.
Not All People Make the Same Sound
Just as not all cultures have the same superstitions about sneezing, not all people make the same noises. It appears the sound you make when you sneeze is related to your culture and what you learn as you grow up. According to partially deaf journalist Charlie Swinbourne,15 those who are deaf from birth sneeze in a more organic fashion, where those who can hear “feel compelled to add sound effects.”
However, those sound effects are not identical from country to country. Those who speak English often sound like “aah-choo,” whereas the French use “atchoum” and the Japanese use “hackashun.” In the Philippines, when sneezing, the individual will verbalize “ha-ching.” Noises made in different cultures may be modified but they are often easily identifiable across cultures.
Do You ACHOO?
Different from the English sound of sneezing, an ACHOO is actually the acronym for autosomal cholinergic helio-ophthalmologic outburst (sometimes also referred to as autosomal-dominant compelling helio-ophthalmic outburst syndrome). For some, bright lights can initiate a burst of sneezing, also called the photic sneeze reflex as discussed in this short video.
German researchers from Saarland University Medical Center discovered this genetic condition after interviewing more than 1,000 people.17 The condition affects between 18 and 35 percent of the population and is transmitted genetically from parent to child, but not along gender lines. In other words, it is not passed specifically to boys or girls.
The condition was traced to a single change in DNA coding, changing a T to a C. The condition is known as a single nucleotide polymorphism, or a single area in your DNA where one nucleotide is different.18 This single change in one nucleotide in DNA triggers your increased sensitivity to light stimulation, resulting in a sneeze.
Science has also found a link between photic sneezing and a gene associated with epileptic seizures induced by light exposure.19 The most current hypothesis of how light triggers sneezing is related to the trigeminal nerve receiving active stimulation from light through the optic nerve and transmitting the stimulation to the maxillary nerve thus causing the tickle you experience right before a sneeze.
Sneezing after entering a well-lit sunny area after being inside is not usually a problem. If you want to reduce the effect, try wearing sunglasses that provide slight protection when you first go outside and remove them after 10 minutes to allow your eyes the health benefits of sunlight.
How Far and Wide They Travel
When you sneeze you release fluid from your nose and mouth, thought to travel between 10 and 100 miles per hour (mph).20,21 The droplets can travel up to 26 feet and stay airborne for minutes.22 In a study performed in Singapore with 10 slender students, researchers measured the speed of a sneeze using high speed cameras.
The researchers acknowledge that while the speed of the students’ sneezes were 10 mph,23 “If somebody did this in the North American setting, with the bigger body frames that they have here, they might find higher velocities." Physicists from the Massachusetts Institute of Technology (MIT) were interested in the spray pattern of sneezing.24
After using high speed cameras to record the release of fluid from mouth and nose, they described a sequence of shapes including sheets, bags and beaded strings of fluid. Knowledge of the progression of this spray may help determine the final spread of droplets, and thus the range over which germs may be spread. The results were presented at the 68th Annual American Physical Society Meeting.25
Don’t Stop a Sneeze
You may be tempted to stop a sneeze, but doctors warn this may cause physical damage.26 Medics in Leicester, Great Britain, attended to a man who attempted to stifle his sneeze by holding his mouth and nose closed. Pressurized air will always take the path of least resistance, which is normally out of your body through your mouth and nose. With this avenue blocked, the highly pressurized air passed up the Eustachian tube and then down the esophagus, ripping through the soft tissue.
While tearing the esophagus may not be immediately painful, the resulting air in the neck area leads to symptoms not often seen in the emergency room.27 The 34 year-old man reported he immediately heard a pop, but it was several hours before he experienced pain in his neck and throat and the quality of his voice changed from the air seeping into the surrounding tissue.28 At this time he visited the hospital where he was admitted for two weeks.
Believing the practice of sneezing was unhygienic, he had been holding sneezes for nearly 30 years. Although rare and unusual for someone to be able to close both nose and mouth enough to force air into the esophagus, case reports in the BMJ warn that trapping a sneeze may cause damage to your eardrums; it could even cause a brain aneurysm.29 A blocked sneeze may also damage your diaphragm or break a blood vessel in the whites of your eye, causing bruising.30
What to Do When You’re in an Awkward Situation
Let’s face it, sometimes when you need to sneeze, the situation can be awkward. You might be in the middle of a large lecture hall, during vows at a wedding or while playing during a band performance like the gentleman in this short video. To stop the spread of bacteria and viruses from coughing and sneezing, the Centers for Disease Control and Prevention (CDC) recommends you sneeze or cough into a disposable tissue and then dispose of the used tissue, followed by washing your hands.31
If you don’t have a tissue handy, sneeze or cough into the crook of your elbow and not your hands or lower on your arm. This deposits germs high up on your clothing where it is less likely they will be transferred to another. If you feel a sneeze on the way and want to nip it in the bud, there are a couple of tricks that won’t cause physical harm and may stop the sneeze.
Dr. Alan Wild, head and neck surgeon at St. Louis University School of Medicine, says if you feel the tickle, you may be able to ward off the sneeze by rubbing your nose, breathing forcefully through your nose or pressing on your upper lip, just below the nose.32 However, once the sneeze has started, it best and safest to just go with the flow.