Your turn
Each lab is one step from the video. Press, drag and pick, and see what happens.
Each lab isolates one part of the story. The models are simplified to show the idea; they are not medical tools.
Tap the buttons and slide the sliders.
Tap the kid (or the button). What jumps when a hiccup hits?
From the outside you see the jolt and hear the sound. The jolt starts with the diaphragm; the sound comes from the vocal cords snapping shut.
Tap the kid. Hic!
Drag the dome down and up. When does air rush in?
Contracting flattens the dome and expands the chest, so air is drawn in; relaxing lets it rise and air flows out.
Slide the muscle down. Air comes in! Slide it up. Air goes out!
Fire a hiccup and watch the timeline. The gate shuts about 35 thousandths of a second after the jerk.
The glottis closes ~35 ms after diaphragm contraction begins, cutting off the inflow. Change the replay speed.
Press the button. The muscle jumps, the gate snaps shut. Hic!
The curves are a simplified model of the timing.
Pick a trigger. Watch the message go up to the brainstem and come back down.
Afferents (vagus, phrenic) carry the signal to the brainstem hiccup centre; efferents fire the diaphragm and close the glottis.
Tap a button. Watch the message zoom to the brain and back!
A simplified map: the real nerves branch much more.
Tap each idea to see its clue. Which one do you find most convincing?
Each hypothesis has supporting evidence; none is proven.
Start a bout, then try a cure, or just wait. Does the cure beat waiting?
Bouts end at random times here, as most do within minutes. Watch how often the last cure tried "gets the credit".
Start the hiccups. Try a trick, or just wait. They stop by themselves!
A toy model, not real data. If hiccups last more than two days, see a doctor.
Hiccups for more than two days? Tell a grown-up and see a doctor.
A hiccup is two quick moves inside you: a jump, and then a snap. It happens all by itself.
Under your lungs is a big, round muscle called the diaphragm. When it pulls down, air comes in. When it goes back up, air goes out.
Sometimes the muscle jumps all by itself. It pulls in a quick gulp of air.
In your throat is a little gate. It slams shut, and the air bumps into it. That's the "hic" sound!
A too-full tummy, from eating fast or fizzy drinks, can start hiccups. So can being very excited. Your tummy sends a message to your brain, and your brain sends back: jump!
A hiccup is an involuntary spasm of your diaphragm, the dome-shaped breathing muscle under your lungs. The spasm makes you suck in a sudden breath. A split second later your vocal cords snap shut, and the air slamming into them makes the "hic" sound.124
The spasm is a reflex. It is most often set off by a stretched stomach, from eating too fast or too much or from fizzy drinks. Excitement, stress and sudden temperature changes can trigger it too.47 Quite often there's no obvious reason at all.3
The diaphragm is a thin, dome-shaped sheet of muscle that separates your chest from your belly. It's your main breathing muscle.25 When it tightens, the dome flattens and pulls down, making more room in your chest, so air flows into your lungs. When it relaxes, it moves back up and the air flows out.513 It works a bit like the plunger in a syringe.
Normally the diaphragm keeps a smooth, steady rhythm. During a hiccup it jerks down suddenly, along with the muscles between your ribs.68 The medical name for hiccups is singultus. It comes from a Latin word for catching your breath while sobbing.6
Every hiccup is really two quick moves:
So the hiccup starts lower down, with the jerk of the diaphragm. The vocal cords in your throat then shut, cutting off the breath and making the noise.13 Once a bout starts, hiccups usually repeat at somewhere between 4 and 60 a minute.9
Doctors list these common triggers for everyday, short-lived hiccups:4236
| Trigger | Why it might set off the reflex |
|---|---|
| Eating too much or too fast | Stretches the stomach, which sits right under the diaphragm |
| Fizzy (carbonated) drinks | Gas bloats the stomach |
| Swallowing air (gum, gulping) | Extra air in the stomach |
| Hot or spicy food | Irritates the food pipe and stomach |
| Excitement, stress, strong emotions | Can set off the reflex; exactly how isn't known |
| Sudden temperature change (hot drink, then ice water) | Can set off the reflex; exactly how isn't known |
The single most common cause is a stretched (distended) stomach.712 The "why it might" column shows the most likely explanations. Scientists still aren't sure exactly how each trigger works.12
Hiccups run on a reflex arc, a nerve loop you don't consciously control, like the knee-jerk reflex.5 Sensors in the stomach, food pipe and chest send signals up the vagus and phrenic nerves to a "hiccup centre" in the brainstem.814 The brainstem fires back. The phrenic nerve jerks the diaphragm, and a branch of the vagus nerve closes the glottis.14 Scientists think the brain has a dedicated rhythm circuit for hiccups, a central pattern generator. It's similar to the circuits for breathing and coughing, which is why hiccups come in repeating bouts.12
Hiccups are common and normal in newborns and infants.15 In fact, they start before birth. Ultrasound scans show hiccups from about nine weeks of pregnancy, before the baby even makes breathing movements.1112 Many pregnant people can feel them as rhythmic little jumps.9 In one study of young infants, a bout of hiccups lasted about 8 minutes on average.15 Hiccups then become less frequent as babies grow.12
Doctors think a baby's hiccups are often set off by extra air in the stomach from feeding.5 But why the reflex exists at all is still an open question. Here are the main ideas and their evidence:
| Idea | The clue | Status |
|---|---|---|
| Breathing practice: hiccups train the breathing muscles before birth | They appear very early, before breathing movements. The idea dates from 1899 and was revived in 1997.9 | Unproven |
| Brain training: hiccups teach the brain how breathing feels | In a 2019 UCL study of 13 newborns, each hiccup set off a burst of brain activity.11 | Unproven (small study) |
| Burp reflex: hiccups push swallowed air out of a milk-drinking baby's stomach | Babies swallow air while feeding, and hiccups seem to happen in most mammals but haven't been described in reptiles, amphibians or birds.9 | Unproven |
| Tadpole leftover: hiccups are an old gill-breathing rhythm | Tadpoles shut their airway while pumping water over their gills. Both rhythms are calmed by carbon dioxide and by the same drug (baclofen).1012 | Unproven |
Bottom line: nobody knows for sure why we hiccup.612 For babies, hiccups are normal. If a baby also coughs a lot or spits up often, parents should check with their paediatrician.5
Yes. Hiccups seem to occur in most mammals.9 Scientists have recorded them in animal studies, and they are easy to spot on ultrasounds of unborn babies.12 Animals hiccup for the same basic reason we do: a quick diaphragm spasm followed by a closed airway.
Everyone has a favourite cure. The NHS lists breathing into a paper bag (never over your head), pulling your knees to your chest, sipping ice-cold water, swallowing some granulated sugar, biting a lemon and holding your breath. It adds that there's no evidence they work for everyone.3 MedlinePlus agrees that there's no proof they work. If you want to try one, ask a grown-up first.2
Why might some help? Holding your breath and breathing into a bag raise carbon dioxide in your blood, and higher carbon dioxide can calm hiccups, though not reliably for everyone.96 Cold water, sugar and lemon may work by stimulating the back of the throat or the vagus nerve.56
There's also a catch. Most bouts stop on their own within minutes anyway.32 So whatever you tried last often gets the credit. A Harvard doctor's favourite cure: wait a few minutes.6
To make hiccups less likely, the NHS suggests avoiding fizzy and very hot drinks, not eating too quickly, and not having something very cold straight after something hot.3
For everyday hiccups, adults and kids share the same triggers. Hiccups that last more than 48 hours are called persistent, and that's when to see a doctor.34 Very long bouts can sometimes be linked to irritation of the vagus or phrenic nerves, other health conditions, or a medicine someone is taking. A doctor can look for the cause.45 Long-lasting hiccups are more common in men than in women.14 Record cases are rare. One Iowa farmer reportedly hiccupped for more than 60 years.6
Your diaphragm, the dome-shaped breathing muscle under your lungs, suddenly twitches and pulls in a quick breath. A split second later your vocal cords snap shut, stopping the air with a 'hic'. The twitch is a reflex, often set off by a stretched stomach, fizzy drinks, eating fast or excitement.
Common repeat triggers are eating or drinking too fast, fizzy or alcoholic drinks, big meals, spicy food, swallowing air (for example chewing gum), stress or excitement, and sudden temperature changes. Often there's no clear reason. If hiccups keep coming back and bother your daily life, talk to a doctor.
Most bouts stop by themselves within a few minutes. Hiccups that last more than 48 hours are called persistent, and that's when you should see a doctor.
Usually nothing: short bouts are normal. Very long-lasting hiccups (more than two days) can sometimes be linked to another health problem or a medicine, which is why doctors want to check them.
Hiccups are common and normal in newborns, and they start in the womb from about nine weeks of pregnancy. Nobody knows exactly why. Ideas include training the breathing muscles, helping the brain learn how breathing feels, and burping out air swallowed while feeding.
There is no proven cure. Some people find that holding their breath, sipping ice-cold water or swallowing a little sugar helps, but health services say no home remedy is proven to work for everyone, so ask a grown-up before trying one. Most hiccups stop on their own within minutes. If they last more than 2 days, see a doctor.
Yes. Hiccups seem to occur in most mammals, and they have been studied in cats, rats, rabbits, dogs and horses. The basic reflex is the same as ours: a quick diaphragm spasm followed by a closed airway.
This page explains how hiccups work. It isn't medical advice: if hiccups last more than two days, see a doctor.