Why Do We Get Hiccups? The Strange Science of an Unexplained Human Reflex

Almost everyone has had them: that sudden, rhythmic "hic — hic — hic" that arrives without warning, interrupts your conversation, resists every remedy you throw at it, and then — just as mysteriously — vanishes on its own. Hiccups are one of the most familiar experiences in human life, yet they remain one of the most poorly understood. Despite centuries of curiosity and decades of modern medicine, no one can fully explain why we hiccup, what purpose the reflex serves, or how to reliably stop it.

The medical name for hiccups is singultus, from the Latin word singult, meaning "the act of catching one's breath while sobbing" — an apt description of the sudden, gasping quality of a hiccup. What we do know is that hiccups involve a remarkably complex reflex arc connecting the brain to the diaphragm through the phrenic and vagus nerves, and that the same reflex appears in every air-breathing mammal — and even in unborn babies. Understanding hiccups reveals the strange gaps that still exist in our knowledge of the human body, and connects us to an evolutionary history stretching back hundreds of millions of years.

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What Is a Hiccup? — The Mechanics

A hiccup is a sudden, involuntary spasm (contraction) of the diaphragm — the dome-shaped muscle that sits just below the lungs and is the main muscle of breathing — followed immediately by the sudden closure of the vocal cords (the glottis). The spasm sucks air into the lungs, and the snapped-shut glottis produces the characteristic "hic" sound. Each hiccup is a complete, two-step event: a powerful inward breath that is cut off almost before it begins.

The Two-Step Sequence

In the first step, the diaphragm and the intercostal muscles (between the ribs) contract sharply, pulling air into the lungs. A fraction of a second later, the glottis — the opening between the vocal cords — slams shut, halting the inflow of air and creating the hiccup sound. The entire sequence lasts less than a third of a second, and hiccup bouts typically repeat at a steady rhythm of about 4 to 60 hiccups per minute.

The Diaphragm — Your Main Breathing Muscle

The diaphragm is the body's principal breathing muscle, a thin, dome-shaped sheet of muscle that separates the chest from the abdomen. When it contracts, it flattens and pulls downward, expanding the chest cavity and drawing air into the lungs. When it relaxes, it rises back up and air is pushed out. Because the diaphragm is critical to breathing, anything that irritates it — or the nerves that control it — can trigger hiccups.

The Intercostal Muscles

The intercostal muscles between the ribs assist the diaphragm in breathing and also contract during a hiccup, which is why you may feel a hiccup as a sudden, full-body jerk of the chest and abdomen rather than just a sound.

The Hiccup Reflex Arc — How It Happens

Hiccups are not a random muscle twitch. They are produced by a reflex arc — a specific neural pathway, first proposed by the physician Philip Bailey in 1943, that connects sensors in the body to the muscles of breathing. Like all reflexes (such as the knee-jerk reflex or the blink reflex), the hiccup arc has three parts: an afferent (sensory) limb, a central processing unit in the brain, and an efferent (motor) limb.

The Three Nerves Involved

The hiccup reflex involves three key nerves:

• The phrenic nerve — the main nerve controlling the diaphragm. It carries motor signals to the diaphragm (telling it to contract) and sensory signals back from it. The phrenic nerves originate in the spinal cord at levels C3–C5 (the third to fifth cervical vertebrae in the neck).
• The vagus nerve — the long "wandering" nerve (from the Latin vagus) that runs from the brainstem down through the neck, chest, and abdomen, supplying the throat, heart, lungs, and digestive tract. Irritation of the vagus nerve anywhere along its course can trigger hiccups.
• The sympathetic nerves (T6–T12) — a chain of nerves in the chest and abdomen that also contribute sensory input to the reflex.

The Central Processing Unit

The signals from these nerves converge on a "hiccup center" in the brainstem (the medulla, near the respiratory centers that control breathing), with additional input from the midbrain and hypothalamus. Because this center has not been precisely located, the exact central mechanism of hiccups remains uncertain — one of the reasons the reflex is so poorly understood.

Neurotransmitters Involved

Research suggests that the neurotransmitters dopamine and GABA (gamma-aminobutyric acid) modulate the hiccup reflex in the brain. This explains why certain drugs that act on these neurotransmitters — such as chlorpromazine (which blocks dopamine) and baclofen (which mimics GABA) — can sometimes stop persistent hiccups.

Why the Reflex Is So Sensitive

Because the hiccup reflex arc passes through so many structures — from the brainstem, down the long vagus nerve, through the chest, to the diaphragm — there are many places where it can be irritated or disrupted. This is why hiccups can be triggered by such a wide variety of causes, from a fizzy drink to a stroke.

What Triggers Hiccups? — Common Causes

Most hiccup bouts are transient, lasting only a few minutes, and arise from everyday triggers that irritate the stomach or the nerves involved in the reflex.

Transient Hiccup Triggers

• Eating too much or too fast — distends (stretches) the stomach, which presses on and irritates the diaphragm and vagus nerve.
• Drinking carbonated beverages — the gas in soda, beer, or sparkling water expands the stomach and irritates the vagus nerve.
• Sudden temperature changes — such as drinking something very hot followed by something very cold.
• Spicy foods — can irritate the stomach lining and the vagus nerve.
• Alcohol — irritates the digestive tract and the nerves involved in the reflex.
• Swallowing air (aerophagia) — from chewing gum, eating too quickly, or drinking through a straw.
• Strong emotions — stress, excitement, anxiety, or even a sudden laugh can trigger hiccups.
• Smoking — irritates the throat and stomach.

These everyday triggers account for the vast majority of hiccup bouts, and they almost always resolve on their own within minutes.

Persistent and Intractable Hiccups — When to Pay Attention

When hiccups last longer than expected, they can signal an underlying medical problem. Doctors classify hiccups by duration:

• Transient — less than 48 hours (the vast majority).
• Persistent — lasting more than 48 hours (over 2 days).
• Intractable — lasting more than a month (in severe cases, for years).

Persistent or intractable hiccups are much less common but far more concerning. They can be caused by conditions that irritate or damage the nerves of the hiccup reflex arc, including gastroesophageal reflux disease (GERD), stroke, brain tumors, kidney failure, diabetes, pericarditis (inflammation around the heart), cancers of the esophagus or stomach, and certain medications (especially steroids, anesthetics, and chemotherapy). Only about 1 in 100,000 people experience intractable hiccups, but for those who do, the cause is often a serious underlying condition that needs medical attention.

The Evolutionary Mystery — Why Do We Hiccup at All?

Here is the strangest fact about hiccups: no one knows why we have them. Most reflexes serve a clear protective purpose — the cough reflex clears the airway, the sneeze expels irritants, the gag reflex prevents choking. But the hiccup reflex has no obvious benefit. So why did evolution preserve it?

The Tadpole and Gill-Breathing Theory

The most fascinating theory connects hiccups to our deep evolutionary past. The neural patterning that generates a hiccup in humans is almost identical to the neural patterning involved in breathing in amphibians — specifically, in tadpoles, which use a similar two-step pumping motion to breathe water through their gills while their lungs are developing. According to this theory, hiccups are an evolutionary leftover from the time when our distant ancestors were transitioning from gill-based breathing in water to lung-based breathing on land. The hiccup reflex may once have helped these early vertebrates pump water over their gills while holding their breath — a useful ability that was preserved in the mammalian lineage long after we lost our gills.

The Fetal Training Theory

Another leading theory focuses on the fact that fetuses hiccup frequently in the womb, beginning as early as the first trimester. Because hiccups are so common before birth, some researchers believe the reflex may serve to train the respiratory muscles for the breathing the baby will need to do after birth — essentially, a built-in exercise program for the diaphragm. This would explain why hiccups are more common in infants than in adults.

The Burping Theory

A third theory suggests that hiccups may once have helped infants burp up trapped air from the stomach, aiding digestion. The coordinated contraction of the diaphragm and closure of the glottis could theoretically help move air upward — useful for a nursing baby whose stomach is often full of swallowed air. This theory would explain why hiccups are most often triggered by a full or distended stomach.

An Evolutionary Leftover

The honest answer is that we do not yet know which of these theories — if any — is correct. Hiccups may simply be an evolutionary leftover, a vestigial reflex that once served a purpose in our ancient ancestors but no longer does. The fact that they cause no harm in most people means evolution has had little reason to eliminate them. Like the appendix or the goosebump reflex, hiccups may be a relic of our deep biological past that we carry with us simply because there was no pressure to lose them.

Hiccups Across Species and Across Life

Hiccups are not unique to humans — and their distribution across species offers some clues to their nature.

All Mammals Hiccup

Pretty much any species that breathes air can hiccup, including all mammals — dogs, cats, horses, mice, and more. Birds and reptiles, by contrast, seem to get a free pass; hiccups have not been documented in them. This pattern supports the idea that hiccups are tied to the specific way mammals breathe and develop.

Fetuses Hiccup — A Lot

Fetuses hiccup frequently in the womb, and pregnant women often feel these rhythmic movements. Fetal hiccuping begins very early in pregnancy and continues throughout gestation. This early and frequent occurrence is one of the strongest pieces of evidence for the fetal training theory: the hiccup reflex is built into our development long before we are born.

Hiccups in Newborns and Infants

Newborns and infants hiccup far more often than adults, sometimes several times a day. This is entirely normal and usually harmless — and, as the fetal training theory suggests, it may play a role in helping the young respiratory system mature. Most babies outgrow frequent hiccuping as they get older.

Why Adults Hiccup Less

As we age, the frequency of hiccups gradually decreases. This may reflect the maturation of the nervous system, changes in eating habits, or simply that the reflex becomes less easily triggered over time. The decline supports the idea that hiccups play a bigger role in early development than in adult life.

The Strange Case of Charles Osborne — 68 Years of Hiccups

To appreciate just how disruptive hiccups can be, consider the most extreme case in recorded history. In 1922, an American farmer named Charles Osborne began hiccuping while attempting to weigh a hog before slaughtering it. The hiccups did not stop — for 68 years. He hiccuped an estimated 430 million times, holding the world record for the longest attack of hiccups.

A Lifetime of Failed Cures

Osborne tried dozens of treatments over the decades, including experimental hormone therapy and even having a friend fire a shotgun behind him to startle him out of it. ("It scared me some," Osborne reportedly said, "but it didn't scare the hiccups out of me.") At the Mayo Clinic, one doctor managed to pause the hiccups by having Osborne breathe a poisonous mixture of carbon monoxide and oxygen — but the cure was worse than the condition, and Osborne could not survive on the gas for long.

Spontaneous Resolution

Remarkably, Osborne's hiccups finally stopped on their own in early 1990, about a year before his death at age 97. The cause of his marathon hiccup bout was never definitively determined, though experts suspect he may have suffered a small stroke — strokes that damage the brainstem can cause persistent hiccups. Osborne's case is a vivid illustration of how disabling intractable hiccups can be: they interfered with his speech, his eating, his sleep, and his work for nearly seven decades.

The Toll of Chronic Hiccups

While cases like Osborne's are extraordinarily rare, even shorter bouts of intractable hiccups can be devastating. Persistent hiccups can disrupt sleep, cause exhaustion and weight loss (from inability to eat), produce significant psychological distress, and seriously impair quality of life. This is why persistent hiccups lasting more than 48 hours warrant medical evaluation.

How to Stop Hiccups — Do Any Remedies Work?

Almost everyone has a favorite hiccup cure, and the list of home remedies is almost endless. The honest truth, however, is that very few hiccup remedies have been scientifically tested, and most have little or no evidence behind them. Still, many people find that certain techniques work for them — possibly because those techniques affect the hiccup reflex arc in ways we do not fully understand.

Remedies That May Work Through Known Mechanisms

Some remedies are thought to work by either increasing carbon dioxide levels in the blood (which can suppress the hiccup reflex) or stimulating the vagus or phrenic nerves to "reset" the reflex. These include:

• Breathing into a paper bag — increases carbon dioxide in the blood, which may calm the diaphragm. (Use caution; never use a plastic bag, and stop if you feel dizzy.)
• Holding your breath — also raises carbon dioxide and may immobilize the diaphragm.
• The supramaximal inspiration technique — exhale completely, take a deep breath and hold for 10 seconds, then take two more small breaths without exhaling, holding each for 5 seconds. This combines elevated CO2, diaphragm immobilization, and positive airway pressure.
• Pulling your knees to your chest and leaning forward — may physically compress the diaphragm and interrupt the spasm.
• Gargling with ice water — stimulates the vagus nerve through the back of the throat.
• Sipping cold water slowly — gentle vagal stimulation.
• Swallowing a spoonful of granulated sugar — the dry texture may stimulate the vagus nerve at the back of the throat.
• Biting into a lemon — the strong sour taste may stimulate the vagus nerve.
• Gently pulling on the tongue — stimulates the vagus nerve.

Remedies With Little Scientific Basis

Many popular remedies — being frightened, drinking water from the far side of the glass, eating a spoonful of peanut butter, having someone press on your eyeballs — have no scientific evidence to support them, though they are generally harmless. They may work for some people through distraction, gentle nerve stimulation, or simply the passage of time (most hiccups stop on their own within a few minutes regardless of what you do).

Medical Treatments for Persistent Hiccups

When hiccups last more than 48 hours, doctors can prescribe medications that act on the hiccup reflex arc. The most commonly used include:

• Chlorpromazine — the only medication specifically FDA-approved for hiccups; it blocks dopamine receptors in the brain.
• Baclofen — a muscle relaxant that mimics GABA and helps calm the diaphragm.
• Gabapentin — affects nerve signaling and is especially useful in patients with cancer-related or central nervous system hiccups.
• Metoclopramide — a prokinetic drug that helps with hiccups related to GERD.

For truly intractable cases, treatments can include phrenic nerve blocks (numbing the nerve that controls the diaphragm), vagus nerve stimulation, and even acupuncture, which has shown some benefit in clinical studies. The most important step, however, is identifying and treating the underlying cause — whether it is GERD, a medication side effect, or a neurological condition.

When to See a Doctor

Most hiccups are harmless and need no medical attention, but persistent or unusual hiccups can sometimes be a sign of an underlying problem worth investigating.

Seek Medical Evaluation If

• Your hiccups last longer than 48 hours (persistent hiccups).
• Your hiccups are severe enough to interfere with eating, sleeping, or breathing.
• Hiccups are accompanied by other symptoms such as chest pain, difficulty swallowing, severe headache, weakness, numbness, or changes in consciousness — these can be signs of stroke, heart problems, or other serious conditions.
• Your hiccups keep coming back frequently in bouts over days or weeks.
• You have an underlying condition (such as GERD, kidney disease, or a recent stroke) and develop new hiccups.

For most people, however, occasional transient hiccups are completely normal and harmless — a small, mysterious quirk of being a mammal with a deep evolutionary history.

FAQ

What causes hiccups?

Hiccups are caused by a sudden, involuntary spasm of the diaphragm followed by the rapid closure of the vocal cords (glottis), producing the characteristic "hic" sound. The spasm is triggered by a reflex arc involving the phrenic nerve (which controls the diaphragm), the vagus nerve (which runs from the brain to the digestive tract), and a processing center in the brainstem. Common everyday triggers include eating too much or too fast, drinking carbonated beverages, swallowing air, alcohol, spicy foods, sudden temperature changes, and strong emotions such as stress or excitement. When hiccups last longer than 48 hours, they can signal an underlying medical condition such as GERD, a stroke, a tumor, kidney failure, or a medication side effect.

Why do we hiccup — what is the purpose?

The honest answer is that no one knows for sure. Unlike most reflexes, the hiccup reflex has no obvious protective function. The leading theories are: (1) the evolutionary leftover theory, which proposes that hiccups are a remnant of the breathing pattern of our ancient amphibian ancestors, who used a similar motion to pump water over their gills — the neural patterning of a hiccup is remarkably similar to respiration in tadpoles; (2) the fetal training theory, which suggests that the reflex exercises the respiratory muscles of fetuses and infants in preparation for breathing after birth (fetuses hiccup frequently in the womb); and (3) the burping theory, which proposes that hiccups once helped infants bring up trapped air from the stomach. Most likely, hiccups are simply a vestigial reflex that once served a purpose but no longer does — a relic of our deep evolutionary past.

How do I get rid of hiccups?

Most hiccups stop on their own within a few minutes, but several techniques may help by either raising carbon dioxide levels in the blood or stimulating the vagus nerve to "reset" the reflex. Techniques with some rationale include breathing into a paper bag, holding your breath, the supramaximal inspiration technique (exhale fully, inhale deeply and hold for 10 seconds, then take two more small breaths and hold each for 5 seconds), pulling your knees to your chest and leaning forward, gargling with ice water, swallowing a spoonful of sugar, and biting into a lemon. Most popular home remedies (being scared, drinking water upside down, eating peanut butter) have little scientific support, but they are generally harmless and may work for some people. If your hiccups last longer than 48 hours, see a doctor — medical treatments such as chlorpromazine, baclofen, or gabapentin can help.

Can hiccups be a sign of something serious?

Usually not — most hiccups are harmless and last only a few minutes. But hiccups that last longer than 48 hours (persistent hiccups) or longer than a month (intractable hiccups) can be a sign of an underlying medical condition. Possible causes include gastroesophageal reflux disease (GERD), stroke, brain tumors, kidney failure, diabetes, pericarditis, cancers of the esophagus or stomach, and certain medications (especially steroids, anesthetics, and chemotherapy). You should seek medical evaluation if your hiccups last more than 2 days, interfere with eating or sleeping, or are accompanied by other symptoms such as chest pain, difficulty swallowing, severe headache, weakness, or changes in consciousness. Only about 1 in 100,000 cases are intractable, but for those, finding and treating the underlying cause is essential.

Do fetuses hiccup in the womb?

Yes — fetuses hiccup frequently, beginning as early as the first trimester of pregnancy, and pregnant women often feel these rhythmic movements. In fact, fetal hiccuping is so common that it is considered a normal sign of development. This early and frequent occurrence is one of the strongest pieces of evidence for the fetal training theory, which suggests that the hiccup reflex exercises the respiratory muscles in preparation for the breathing the baby will need to do after birth. Newborns and infants also hiccup far more often than adults — sometimes several times a day — which is entirely normal and usually harmless.

Do animals get hiccups?

Yes. All mammals — including dogs, cats, horses, mice, and others — can hiccup, because they have the same diaphragm, phrenic nerve, and brainstem structures that produce the reflex in humans. Birds and reptiles, however, do not appear to hiccup. This pattern supports the idea that hiccups are tied to the specific way mammals breathe and develop, and possibly to our shared evolutionary history with other air-breathing vertebrates. If you have a puppy or kitten at home, you may have noticed them hiccuping — this is completely normal and usually harmless, just as it is in human infants.

What was the longest case of hiccups ever recorded?

The longest recorded attack of hiccups lasted 68 years. The sufferer was an American farmer named Charles Osborne, who began hiccuping in 1922 while attempting to weigh a hog before slaughtering it. His hiccups did not stop until 1990, about a year before his death at age 97 — by which point he had hiccuped an estimated 430 million times. Osborne tried dozens of cures, including a (temporary and dangerous) treatment with carbon monoxide at the Mayo Clinic, but nothing worked until the hiccups resolved spontaneously. Experts suspect the cause may have been a small stroke affecting the brainstem. His case vividly illustrates how disabling intractable hiccups can be — they interfered with his speech, eating, sleep, and work for nearly seven decades.

References

• Chang FY and Lu CL: Hiccup — mystery, nature, and treatment — the hiccup reflex arc and clinical management (Journal of Neurogastroenterology and Motility, PMC, 2012; updated reviews 2023).
• StatPearls (NCBI): Singultus — classification of acute, persistent, and intractable hiccups and etiologies (updated 2024).
• WebMD: Remedies for Hiccups — what to do and when to see a doctor (updated 2024).
• Cleveland Clinic: Hiccups — causes and ways to get rid of them (updated 2024).
• Howland RH: Hiccup — a treatment overview — pharmacotherapy with chlorpromazine, baclofen, and gabapentin (Journal of Clinical Psychopharmacology; updated reviews 2023).
• Straus C, Vasilakos K, and Wilson RJA: A phylogenetic hypothesis for hiccup — the amphibian and tadpole connection (Advances in Experimental Medicine and Biology; updated reviews 2023).
• Sloan M: What is the purpose of hiccuping? — evolutionary theories and the Charles Osborne case (Discover Magazine, 2023).
• MedlinePlus and Penn State Health: Hiccups — causes, myths, and when to seek medical care (updated 2024).
• National Health Service (NHS) and BBC Bitesize: Hiccups — home remedies and self-care guidance (updated 2024).
• Smith HS and Busracamwongs A: Management of hiccups in therapeutic settings — pharmacological and non-pharmacological approaches (Journal of Pain and Palliative Care Pharmacotherapy; updated reviews 2023).

This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Most hiccups are harmless and resolve on their own, but if your hiccups last longer than 48 hours, interfere with eating or sleeping, or are accompanied by other concerning symptoms, please consult a qualified healthcare provider.