Explainer: what, exactly, is a hiccup?

Hiccups are very odd quirks of our anatomy. We don’t fully understand what causes them, or what purpose they serve, and we certainly don’t have a clear answer on what stops them.

And yet, there’s still scientific research happening on hiccups. Here are some of Cosmos’ favourite (sort of) peer reviewed hiccup cures.

What are hiccups?

Hiccups – scientific term singultus – are primarily the fault of two parts of our body: the diaphragm and the epiglottis.

The diaphragm is a big muscle below your lungs. It’s the major reason you breathe – as it contracts and expands, air gets pulled in and pushed out of your lungs.

The epiglottis is a small flap of tissue that sits at the top of your windpipe, flipping shut when you’re eating so that you don’t inhale food or liquid.

Hiccups happen when the diaphragm spasms. This sudden movement sucks air into the lungs quickly, and your epiglottis slams shut. The ‘hic’ sound is caused by the epiglottis closing the door.

Other animals with diaphragms can also hiccup – including cats, rats, rabbits and dogs.

What causes them?

It’s not clear what causes these spasms in the diaphragm – they’re controlled by the nervous system, but what triggers our nerves?

The exact mechanisms aren’t obvious. Food and drink are often triggers – particularly fizzy drinks, alcohol, hot food, or eating too quickly.

Other common triggers include smoking, stress, and pregnancy – but hiccups can happen independently of any of these.

Can they be cured?

Many doctors’ recommendations for hiccup cures are not too different to home remedies – things like holding your breath, breathing deeply, or eating: sugar, honey, ice, or something sharp like ginger, lemon or vinegar.

In the medical literature, there are dozens and dozens of case studies showing one thing or another works. Broader data is sparse – because they usually only last a few minutes, it’s hard to run a clinical trial on hiccups. Most studies involve chronic hiccuppers, who may have underlying conditions that make their hiccups different.

One cure favoured by bartenders is quickly eating a lemon wedge soaked in bitters, much like you would an orange slice. A 1981 study in the New England Journal of Medicine, done by a doctor and a bartender, found that this worked in 14 out of their 16 volunteers, all of whom got hiccups when they were drunk.

Another claim, desperately wanting peer review, appears in the Journal of the American Medical Association in 1966.

The method proposes putting a spoon, fork or other metal object in a glass of water, and holding the metal against the temple while sipping from the glass. The writer claims he’s being getting people to do it for nearly 30 years and it has never failed him.

“I have not been able to arrive at a reasonable explanation, physiological or otherwise, which would throw any light upon the manner in which the desired effect is achieved,” he writes.

“Necromancy has been suggested, but I gravely doubt it.”

The editors of the journal are unconvinced by this letter – and it’s worth noting the writer, Ashley Montagu, holds his qualifications in natural selection and ecology.

In 2000, another case study reported a man who’d had persistent hiccups for four days following treatment for back pain – but they stopped when he had sex with his wife. Specifically, they stopped at the climax of the session, and he didn’t have another case of hiccups for at least a year.

Something with a more reliable body of evidence behind it is a device made specifically to stop hiccups: the ‘Hiccaway’ straw. This straw is designed to make people contract their diaphragm when they use it, and a study with 290 regular hiccuppers found they rated it better than home remedies.

Ultimately, because most hiccups go away after a few minutes, the only infallible cure is to wait them out. If you’re doing something when your hiccups stop, it’s possible that worked – or maybe that’s just what you were doing when your hiccups stopped.

What about chronic hiccups?

Hiccups that last longer than 48 hours can be a sign of an underlying condition – like a lung or kidney disease, or brain damage in the area of the brain that controls the diaphragm. They can also be a side effect of medications, like anti-epileptics.

Chronic hiccups can be remedied by addressing the root cause. Alternatively, anti-nausea medications like chlorpromazine (branded Largactil in Australia) can soothe chronic hiccups.

In serious cases, people might need surgery to the nerves that control the diaphragm. This used to be done by severing the nerves permanently, but recently researchers have come up with more reversible ways to tie the nerves shut in surgery.