What does sneezing do?

Contents

How To Sneeze Properly

Achoo! Sneezing creates particles of snot that can transfer infections. Inf-Lite Teacher/Flickr BI Answers: What is the best way to sneeze?

It’s spring, that wonderful season of allergies.

And with allergies comes sneezing.

In addition to allergies, sneezing can be caused by being too full, bright lights, and even orgasms. But as common as sneezing is — other animals sneeze too — scientists know little about the phenomenon.

“A sneeze is designed to expel foreign particles and irritants from your airway, particularly your nasal cavity, and is a protective reflex,” Dr. Jonathan Moss of the Charlotte Eye, Ear, Nose & Throat Associates told Business Insider.

With sneezing myths running rampant on the Internet, we decided to put the following questions to the experts.

Which Way’s the Exit?

If the sneeze is supposed to clean out our noses, should we let it out our mouths too? Sure, said Moss.

“The goal is to expel the irritant from the nasal cavity,” said Moss, so it’s important to sneeze at least partly out of your nose.

However, because the nasal cavity isn’t big enough alone to handle the release of such a large volume of air, some of the sneeze pretty much has to go out your mouth. “The caveat being that if someone tries to withhold a sneeze, this volume will be lessened and the mouth could remain closed,” Moss said.

Holding It In vs. Letting It Out

The most common mistake people make when sneezing is just that — trying to hold it in.

“Don’t!” said Moss. “The process of sneezing is a defensive reflex. The body has to expel foreign particles, such as dust or pollen, that enter our upper airway.”

Because a sneeze causes high pressures in your internal airways, holding it in can be harmful. But it causes problems only in rare situations. “These complications can include hearing loss, forcing air into the eye or brain, rupture or clotting of blood vessels, or breaking a rib,” Moss said.

And keeping your eyes open when you sneeze? It’s possible.

Once the “sneeze center of the brainstem” has been stimulated, it sends multiple muscle contraction signals to your body. One of them tells your eyes to close. “While it may not be impossible to keep from closing your eyes, it would take a conscious effort to keep them open,” Moss said.

The Best Sneeze Interceptor

All in all, a sneeze may be annoying, but it is good for you. “In our society, some may consider sneezing a faux pas, but what I typically tell my patients is to let it fly!”

The only problem is that these sneezes can spread germs to others around you.

While a few media outlets have done home experiments putting sneeze barriers to the test, scientists have been busy in the lab trying to figure out the best way to sneeze in order to stop the germ flow.

“Ambient air currents may also move the sneezed airflow around more slowly later, thus transporting airborne viruses beyond the immediate vicinity of the sneezer,” Dr. Julian W. Tang of the Alberta Provincial Laboratory for Public Health told Business Insider.

He’s conducted experiments — seen in the GIFs below — to find out the proper way to catch your sneeze.

So, is it the open-hand catch?

Or the wait-was-that-a-cough open fist?

Or the quick-quick-grab-a-tissue?

“Lots of tissues,” Tang said, and wash your hands after.

No matter the sneeze catcher, the amount of snot stopped has “a lot of it has to do with how fast you can cover your sneeze.”

The permeability of the barrier used to catch the sneeze is also important. “Lower-ply tissues may not contain the force of the sneeze that may just blow through the tissue,” he said.

When using the hand or fist, it is important to note that any gaps between fingers will spread the sneeze.

Sneezing into your sleeve has variable effectiveness, depending on sleeve length and how fast you can cover up. And the sleeve now contains your germs, which can spread to other objects it comes into contact with.

So let it fly — into a tissue, please.

This post is part of a continuing series that answers all of your “why” questions related to science. Have your own question? Email [email protected] with the subject line “Q&A”; tweet your question to @BI_Science; or post to our Facebook page.

Don’t hold your nose and close your mouth when you sneeze, doctors warn

One young man managed to rupture the back of his throat during this manoeuvre, leaving him barely able to speak or swallow, and in considerable pain.

Spontaneous rupture of the back of the throat is rare, and usually caused by trauma, or sometimes by vomiting, retching or heavy coughing, so the 34 year old’s symptoms initially surprised the emergency care doctors.

The young man explained that he had developed a popping sensation in his neck which immediately swelled up after he tried to contain a forceful sneeze by pinching his nose and keeping his mouth clamped shut at the same time.

A little later he found it extremely painful to swallow and all but lost his voice.

When the doctors examined him they heard popping and crackling sounds (crepitus), which extended from his neck all the way down to his ribcage — a sure sign that air bubbles had found their way into the deep tissue and muscles of the chest, which was subsequently confirmed by a computed tomography scan.

Because of the risk of serious complications, the man was admitted to hospital, where he was fed by tube and given intravenous antibiotics until the swelling and pain had subsided.

After seven days he was well enough to be discharged with the advice not to block both nostrils when sneezing in future.

“Halting sneezing via blocking nostrils and mouth is a dangerous manoeuvre, and should be avoided,” caution the authors.

“It may lead to numerous complications, such as pseudomediastinum , perforation of the tympanic membrane , and even rupture of a cerebral aneurysm ,” they explain.

Why Do We Sneeze?

Not all sneezes happen when foreign substances enter our nostrils. Sometimes, we find ourselves bracing for a sneeze’s impact at unusual moments.

Why do we close our eyes when we sneeze?

Closing your eyes is a natural reflex your body has each time you sneeze. Despite common lore, leaving your eyes open while you sneeze will not cause your eyes to pop out of your head.

Why do we sneeze when we’re sick?

Just like our body tries to clear house when a foreign substance enters the body, it also tries to eliminate things when we’re sick. Allergies, the flu, a common cold — they can all cause a runny nose or sinus drainage. When these are present, you may experience more frequent sneezing as the body works to remove the fluids.

Why do we sneeze when we have allergies?

Dust stirred up while cleaning may make anyone sneeze. But if you are allergic to dust, you may find yourself sneezing more often when you clean because of how frequently you come into contact with dust.

The same is true for pollen, pollution, dander, mold, and other allergens. When these substances enter the body, the body responds by releasing histamine to attack the invading allergens. Histamine triggers an allergic reaction, and symptoms include sneezing, runny eyes, coughing, and runny nose.

Why do we sneeze when looking at the sun?

If you walk out into the day’s bright sun and find yourself close to a sneeze, you’re not alone. According to the National Institutes of Health, the tendency to sneeze when looking at a bright light affects up to one third of the population. This phenomenon is known as photic sneeze reflex or solar sneeze reflex.

Why do some people sneeze multiple times?

Researchers aren’t sure why some people sneeze multiple times. It may be a sign that your sneezes aren’t quite as strong as a person who only sneezes once. It could also be a sign that you have ongoing or chronic nasal stimulation or inflammation, possibly as a result of allergies.

Can orgasms cause sneezes?

Indeed, it’s possible. Researchers have discovered that some people sneeze when they have sexual thoughts or when they orgasm. It’s not clear how the two things are connected.

Why Do Some Of Us Sneeze Multiple Times In A Row?

Here’s looking achooo kid…

“My father sneezes 16 times in a row, every time,” boasted ten daily’s Deputy Editor this morning, when one of the news team sneezed three times in quick succession.

Which got us thinking. Why? Why is it that some people sneeze just one small ladylike “achoo” while others blast out a machine-gun like staccato of sneezes, and others simply can’t do a single sneeze but have a tissue-filling trio at every turn?

Here’s what we found out.

There are a number of irritants that can trigger a sneeze. Viral respiratory infections, such as the common cold, can irritate the mucous membrane in your nose. So can cold air; allergens, such as pollen and pets; physical irritants, including smoke and pollution; and environmental particles, such as dust, mildew and mould.

For people who sneeze three times, for example, in quick succession, doctors seem to all agree that one sneeze probably loosens whatever is irritating it, the second sneeze gets it to the front of the nose and the third sneeze gets it out. For those who sneeze more than that, keep reading.

Not all sneezing is irritant-related. Some people sneeze when they go out into the sun, thanks to a condition known as photic sneezing. Other people sneeze when they eat spicy food — this is Gustatory Rhinitis, a type of nonallergic Rhinitis that’s caused by eating certain foods or sometimes drinking alcohol. Others sneeze when their stomach is full — a condition known as “snatiation” — and yes, while the name is kind of a joke, that is a real thing.

You see “snatiation” is a combination of the words “sneeze” and “satiation,” (did you, erm, pick it?) which means being full or satisfied. It refers to a relatively common condition that causes people to sneeze uncontrollably after a large meal.

Got it? Bless you.

Now, we’re not alone in our curiosity. Reddit is filled with similar questions — why do I sneeze three times, or why does my husband sneeze so much, so often, so hard, for example.

And one user, MacGyverMacGuffin is our new nasal hero, giving us this info on sneezing and answering all our questions at once (including why some people sneeze a whopping 16 times each go).

“Sneezing is usually caused by nasal irritation. Once the signal is sent from the nose to the brain and the rest of the nervous system, a sneeze develops as an automatic response across many parts of the body. One good sneeze may be enough to get the irritant off the nasal mucosa, but the nervous system may still think it needs to sneeze, as the chemicals that sent the signal (histamines) may still be sending the signal. If so, it will keep making a person sneeze involuntarily until the signal finally stops firing.”

In many ways, especially when nerves are involved, your body can have a mind of its own sometimes. Given that the body may have a common amount of time until the signal stops, some people may commonly sneeze a specific number of times on average.”

He continues, “Many different parts of the body are involved in a sneeze. It could have something to do with the specific volume of air a person’s lungs can hold in comparison to the total amount of sneeze-force a nose usually needs to get irritants off its mucosal lining. It could also just be a habit your brain or nerves have learned over time, much like the phenomenon of “muscle memory”.”

When asked by another Redditer why it was that they only sneeze twice in a roow, never three times he replied:

“Because your overall bodily system found two sneezes to be most often the right number, and your central nervous system developed a habit through muscle memory of doing exactly two in response to any irritant.”

So some people’s bodies think 16 times is the right number, see?

Ah science.

Gesundheit.

Image: Getty

Feature Image: Getty

The tendency of some people to sneeze in response to bright light wasn’t only just noticed in the last century; the Greek philosopher and scientist Aristotle observed the phenomenon as well. In his Book of Problems, he (or possibly his students) asked, “why does the heat of the Sun provoke sneezing, and not the heat of the fire?” He concluded that the Sun’s heat aerosolises the fluids within the nose, which triggers a sneeze. The heat of a fire, on the other hand, not only vaporises those fluids, but also consumes them, thus drying out the nose, which actually inhibits a sneeze.

Never mind that he wasn’t exactly spot on either in the cause for the sunny sneeze – it’s light, not heat – nor in the explanation, but it means that the reflex was known to some perhaps as early as the third century BC.

Bright lights, big sneeze

We now know quite a bit more about the biology that underlies the photic sneeze reflex. For example, the reflex is now also known by the hilariously apt acronym Achoo, which stands for Autosomal Dominant Compelling Helio-opthalmic Outburst. “Autosomal” because the affiliated gene is located on one of the non-sex-linked chromosomes, and “dominant” because you only need to inherit it from one of your parents to express the trait.

In 2010, a group of geneticists led by Nicholas Eriksson of the genetic testing company 23andMe identified two single nucleotide polymorphisms, or SNPs, that were associated with the sunny sneeze by assessing the genotypes of nearly 10,000 23andMe customers. These SNPs are alterations to single letters within a person’s genetic library. One is called rs10427255 and the other, about which there is somewhat less statistical certainty, is called rs11856995. One of them is located nearby a gene known to be involved in light-induced epileptic seizures, which raises the possibility that there might be some kind of biological link between the two syndromes.

Why We Sneeze, and Other Fun Facts About Sneezing

A sneeze can be a wet, slimy mess. It can be a tiny toot. It can happen when we’re allergic, sick, staring at a bright light — or, compulsively, when we’re anxious.

Why do we sneeze? Simply put, a sneeze is the best way for the body to clear its passages so you can keep breathing clean air.

But what causes sneezing? When irritants such as mucus from a cold or the flu, germs, dust, pollen, animal dander, or pollutants — just to name just a few — infiltrate the nose lining, you take a massive inhalation.

Then the chest muscles tighten and pressure builds. The tongue pushes against the roof of the mouth, forcing breath to come out fast through the nose, and — achoo!

Sneezing can be annoying, fun … and funny. About one in four people feel the need to sneeze when they look at a bright light. Others sneeze after orgasm (and some associate the relief of sneezing with sexual release). Still others sneeze when the neighbor’s dog nuzzles them or when spring pollen fills the air.

But the big “achoo” usually isn’t very sexy. In fact, according to the Mayo Clinic, the expelled air from one sneeze can reach speeds of 30 to 40 mph or more. Talk about nasal warfare.

So it’s not surprising that sneezing, which transmits nasal droplets and saliva through the air, is one of the primary ways infectious diseases — including cold and flu viruses — are transmitted. That’s why people are told to sneeze into a tissue or their elbows during cold and flu season.

In addition, the Centers for Disease Control and Prevention (CDC) reminds us to wash our hands with soap and water after sneezing and throughout the day, particularly after using the bathroom and before eating. If soap and water are not available, use an alcohol-based hand sanitizer that contains at least 60 percent alcohol to clean your hands.

Sneezing is one of the main symptoms of a common cold. Other cold symptoms include:

  • Congestion
  • Cough
  • Generally feeling unwell (malaise)
  • Low-grade fever
  • Runny or stuffy nose
  • Slight body aches or a mild headache
  • Sore throat

Sneezing is also a main symptom of hay fever or allergic rhinitis, along with the following:

  • Itching of the nose, eyes, or roof of the mouth
  • Runny, stuffy nose
  • Watery, red or swollen eyes (conjunctivitis)

If you feel the need to sneeze but don’t want to, try looking away from the light, pressing your tongue to the top of your mouth, breathing deeply, or preemptively blowing your nose. Here are other fun and surprising facts about sneezing.

Everyday Mysteries

Question Does your heart stop when you sneeze?

No, your heart does not stop when you sneeze.

Edison Kinetoscopic record of a sneeze. Print shows a man, Edison engineer Fred Ott, sneezing. The accompanying Harper’s Weekly article describes the image as “the entire record of a sneeze from the first taking of a pinch of snuff to the recover” using “eight-one prints taken in about two seconds.” Prints & Photographs Division, Library of Congress.

A sneeze begins with a tickling sensation in the nerve endings that sends a message to your brain that it needs to rid itself of something irritating the lining of your nose. You first take a deep breath and hold it, which tightens your chest muscles. The pressure of air in your lungs increases, you close your eyes, your tongue presses against the roof of your mouth and suddenly your breath comes out fast through your nose.

Ah–tchi: ou Rhume de cerveau. Caricature: a man is sneezing into a handkerchief. National Library of Medicine Digital Collections.

So where did the myth originate that your heart stops when you sneeze? The changing pressure in your chest due to sneezing also changes your blood flow, which may change the rhythm of your heartbeat. Dr. Richard Conti, past president of the American College of Cardiology, speculates that the belief that the heart actually comes to a stop during a sneeze could result from the sensation of having the heart “skip a beat.” When there is a prolonged delay before the heart’s next beat, he said, that beat is then more forceful and more noticeable, perhaps as a funny sensation in the throat or upper chest (Ray, 1992).

Poster ad for Arrow Handkerchiefs. Prints & Photographs Division, Library of Congress.

Why do people say, “God bless you,” after someone sneezes?

There are varying accounts as to the origin of this response. One belief is that it originated in Rome when the bubonic plague was raging through Europe. One of the symptoms of the plague was coughing and sneezing, and it is believed that Pope Gregory I (Gregory the Great) suggested saying “God bless you” after a person sneezed in hopes that this prayer would protect them from an otherwise certain death.

The expression may have also originated from superstition. Some people believe that the custom of asking for God’s blessing began when ancient man thought that the soul was in the form of air and resided in the body’s head. A sneeze, therefore, might accidentally expel the spirit from the body unless God blessed you and prevented this from occurring. Some ancient cultures also thought that sneezing forced evil spirits out of the body endangering others because these spirits might now enter their bodies. The blessing was bestowed to protect both the person who sneezed and others around him.

Woman in a lace dress waving a handkerchief, c1900. Prints & Photographs Division, Library of Congress.

Sneeze responses from around the world:

English – “Bless you” or “God bless you”
German – “Gesundheit”
Greeks and Romans – “Banish the Omen”
Hindu – “Live” and responds “With you”
Zulu – “I am now blessed”

Interesting facts:

  • Sneezes are an automatic reflex that can’t be stopped once sneezing starts.
  • Sneezes can travel at a speed of 100 miles per hour and the wet spray can radiate five feet.
  • People don’t sneeze when they are asleep because the nerves involved in nerve reflex are also resting.
  • Between 18 and 35% of the population sneezes when exposed to sudden bright light.
  • Some people sneeze when plucking their eyebrows because the nerve endings in the face are irritated and then fire an impulse that reaches the nasal nerve.
  • Donna Griffiths from Worcestershire, England sneezed for 978 days, sneezing once every minute at the beginning. This is the longest sneezing episode on record.

“Do not sneeze in your gas mask,” The Stars and Stripes, February 15, 1918, page 7. Library of Congress

Pamela Georgeson D.O., a member of the American Osteopathic Association, is a board-certified osteopathic physician in pediatrics, as well as in allergy and immunology. She gives the following answer:

Image: UNIVERSITY OF ARIZONA MITES are among any number of allergens that can trigger sneezing.

Sneeze: to make a sudden violent spasmodic audible expiration of breath through the nose and mouth, especially as a reflex act.

The nose provides the main route through which inhaled air enters and leaves the lower airways. Because of its position, it serves numerous functions. The narrowing passageways cause inspired air to flow with increased turbulence. This turbulence in turn increases the interaction between the airstream and the nasal mucosa (lining of the nose), allowing for heat and moisture to be exchanged, and for suspended or soluble particles from the air to be cleared.

Sneezing is a physiologic response to the irritation of the respiratory epithelium lining of the nose. The process usually begins with the release of chemicals such as histamine or leukotrienes. These substances are manufactured by inflammatory cells such as eosinophils and mast cells typically found within the nasal mucosa. Chemical release is caused by viral respiratory infections, filtered particles, allergens (substances that trigger allergic reactions) or physical irritants such as smoke, pollution, perfumes and cold air. Allergic reactions with the nasal mucosa require the presence of IgE (allergy antibody specific for the allergen). This leads to fluid leakage from vessels in the nose, causing symptoms of congestion and nasal drip. Additionally, nerve endings are stimulated, leading to the sensation of itching.

Ultimately, the nerve ending stimulation leads to activation of a reflex inside the brain. The nervous impulse travels up the sensory nerves and down the nerves controlling muscles in the head and neck, and that leads to the rapid expulsion of air. The high velocity of the airflow is achieved by the buildup of pressure inside the chest with the vocal chords closed. Sudden opening of the cords allows the pressurized air to flow back up the respiratory tract to expel the irritants. This helps to remove offending particles in the nose. However, in infected individuals, it also allows for the spread of the common cold, as innumerable viral particles are contained within each droplet of mucus expelled.

Various medications are available to help control this reaction. Antihistamines act principally by blocking the action of histamine at receptors located on the blood vessels in the nose. Some prescription antihistamines are nonsedating, compared with their over-the-counter counterparts. Decongestants stimulate receptors located on the same vessels to cause constriction and lessen the congestion. Topical nasal steroids are used in allergic patients to reduce the number of inflammatory cells and ultimately inhibit the release of histamine.

What to know about making yourself sneeze

The following tips to induce sneezing work by activating the nerves that trigger the body to sneeze.

1. Use a tissue

Roll the corner of a tissue into a point, and place it in one nostril. Gently move the tissue back and forth, until feeling a tickling sensation. This action stimulates the trigeminal nerve.

It is essential to take care when using this technique — do not insert the tissue too far up the nostril as it may cause pain.

2. Tickle with a feather

Some people can be induced to sneeze by simply brushing underneath the nose with a fake feather. It is not recommended to use a real feather, nor to insert the feather into the nose.

3. Look at the light

Share on PinterestIn some people, looking suddenly at a bright light may induce sneezing.

Some people can sneeze on demand just by looking at a bright light. Researchers estimate that up to a third of the population are susceptible to this form of reflexive sneezing, which is known as photic sneeze reflex (PSR) or ACHOO (autosomal dominant compulsive helio-ophthalmic outbursts of sneezing). This reflex may occur because the trigeminal nerve is located beside the optic nerve.

Photic sneezing is hereditary — if one parent is affected, their child has a 50 percent chance of also having the reflex.

Those who wish to try this should look at a bright light suddenly. However, never look directly at the sun, as this can cause damage to the eyes.

4. Sniff strong perfume

Some strong perfumes and colognes can cause people to sneeze. To try this, spray a strong fragrance in the air to irritate the nasal lining.

Do not inhale the perfume particles directly, and never spray the fragrance directly into the nostril.

5. Tweeze a nostril hair

Plucking out a single nostril hair can stimulate the trigeminal nerve to cause a sneeze. Be gentle though, as the skin in the nostrils is extremely sensitive.

6. Eat dark chocolate

Dark chocolate with a high percentage of cocoa may lead to sneezing. The exact reason for this occurrence is not known, but scientists do not think it has anything to do with allergies.

While this tip certainly won’t work for everyone, it does work for some — particularly those who do not regularly eat chocolate.

7. Tilt the head back

This technique may be especially beneficial for those who feel a sneeze coming on, but it does not quite materialize. Simply lean the head back and look upwards.

8. Smell spices

Share on PinterestSpices may irritate the mucous membranes and induce sneezing, although they may cause a burning sensation in the nostrils.

Black pepper and other spices — such as cumin, coriander, and crushed red pepper — are known nasal irritants. A compound in both black and white pepper contains piperine, which irritates the mucous membranes. Likewise, capsaicin — a natural component of hot peppers — will cause a sneezing reaction.

Try opening a jar of spices and taking a gentle sniff, or grind up some whole peppercorns to induce a sneeze. Cooking spicy food or inhaling some capsaicin extract from a bottle may also work.

Take care when smelling spices as inhaling too much can lead to a burning sensation in the nostrils.

9. Pluck an eyebrow hair

Similarly, tweezing the brows can irritate the facial nerves, which may stimulate the trigeminal nerve. Some people sneeze after plucking a single hair, while others need to tweeze a few.

10. Use the tip of the tongue

Lightly run the tip of the tongue up and down the roof of the mouth. The trigeminal nerve runs along this path. A person may have to experiment regarding the best place to massage, the level of pressure to apply, and the amount of time taken to induce a sneeze.

11. Massage the nose

Gently rub the bridge of the nose in a downward motion to get a response from the trigeminal nerve. Some people may get results from lightly pinching the nose. Again, experiment with technique until a tickling sensation and a sneeze occur.

12. Get some cold air

Cold air to the face can trigger the sneeze reflex. Go to a cold area and take in some deep breaths of cool air. If it is not cold outside, turn up the air conditioning or open the freezer and breathe in the cold air.

13. Have a carbonated drink

A receptor on the tongue, known as the TRPA1 receptor, is activated by the carbon dioxide in fizzy drinks. When several receptors are stimulated, the body increases saliva and triggers a cough or sneeze.

Inhaling the bubbles also works because the nose is more sensitive than the tongue to carbon dioxide.

People’s sneezing tendencies can be almost as individual as their fingerprints. Some produce earth-shattering blasts. Others emit delicate “ahchoos!” But why do we sneeze in the first place? No matter where you fall on the sneezing spectrum, the answer is more interesting than you might expect and will leave you pretty impressed with your body.

Sneezing helps to clear unwelcome stuff from your nose.

As one entrance to your complex respiratory system, your nose has the important job of humidifying, warming, and filtering the air you breathe, according to the Merck Manual. That makes your nose one of the first lines of defense for keeping potentially harmful particles out of your lungs, Erich Voigt, M.D., clinical associate professor and chief of general/sleep otolaryngology at NYU Langone Health, tells SELF. Your nose is lined with mucous membranes that constantly trap pathogens and debris. Cilia, microscopic hairlike protrusions lining your nose, can channel this dirty mucus to the front of the organ (or down your throat).

But sometimes something triggers your nose intensely enough that your body wants to expel it forcefully and immediately, so this ordinary cleansing process gets an instant boost in the form of a sneeze. “The sneeze serves as a mechanism to clean the nose” and stimulate the cilia to keep things moving along, Michael Benninger, M.D., chairman of the Cleveland Clinic Head & Neck Institute, tells SELF. “It’s basically rebooting the nose,” he says.

The sneeze reflex is usually activated when your nose’s mucous membranes are irritated.

Sometimes it can happen if your throat is irritated, too. Either way, sneezing is “a well-coordinated action involving a lot of muscles and nerves beginning with a trigger,” Dr. Voigt explains.

The most common triggers are pathogens (like the common cold and flu viruses), allergens (like pollen or cat dander), and irritants, which can be chemical (like perfume) or physical (like dust), Dr. Voigt says.

In some cases, as with allergens and viruses, the trigger is not just the matter itself but the nose’s inflammatory response to it, Dr. Benninger says. Both allergic and nonallergic rhinitis (inflammation of the mucosal lining of the nose) can result in membrane swelling and excess mucus, potentially triggering sneezing. In the case of allergies, chemicals like histamine, which your immune system produces in response to an allergen, can also induce sneezing.

Here’s how the actual sneezing process goes down.

First, a foreign particle stimulates the trigeminal nerve, the largest nerve connecting to the brain. This sensory nerve provides feeling to numerous areas on the face and head, including the mucosal lining of the nose, mouth, and sinus cavities, as well as the skin, teeth, and back of the tongue.

Once stimulated, the trigeminal nerve relays a message to the brain, which then sends out various action signals to the body, Dr. Voigt explains. If your brain receives the message that an intruder is in your nose, your diaphragm tightens and moves down so your lungs can fill with air, your throat muscles relax, your mouth opens, your eyes close, and you sneeze. “The whole point is to generate pressure from our lungs to blow out what’s in our nose,” Dr. Voigt explains.

It’s also possible that there’s more going on here than science has yet unveiled. Although the trigeminal nerve is probably the predominant mechanism involved in most sneezes, Dr. Benninger says that there are likely other mechanisms at play that we don’t entirely understand, such as the involvement of other cranial nerves.

People can also sneeze in reaction to non-nose triggers.

One of the more well-studied examples is exposure to bright lights, a phenomenon called photic sneezing. Then, of course, there’s the wild occurrence of sneezing when you apply mascara or pluck your eyebrows. People have also been reported to sneeze during or after an orgasm. Sneezing can even result from strong emotions in some people, according to the U.S. National Library of Medicine.

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