Hiccups

How it works

The diaphragm is the sheet of muscle under the lungs. It pulls down to draw air in³. A hiccup starts when the diaphragm contracts suddenly and without warning. Air rushes into the throat. A split second later the glottis, the opening between the vocal cords, snaps shut. The rush of air stops dead against the closed cords. That makes the “hic”¹.

The reflex runs through the phrenic and vagus nerves and a control centre in the brainstem¹. Common triggers are eating too fast, a full stomach, fizzy drinks, alcohol, sudden excitement, and a quick change in temperature¹. Babies hiccup in the womb, and newborns hiccup often¹.

A normal bout lasts a few minutes and stops on its own. Hiccups that last more than 48 hours are called persistent¹. Bouts that go on for more than a month are called intractable¹. These are rare, at roughly 1 in 100,000 people per year, and they usually have a medical cause¹.

No one knows what hiccups are for. One hypothesis, put forward by Straus and colleagues in 2003, is that the reflex is a leftover from our distant ancestors¹. Tadpoles and some amphibians breathe by gulping water through the mouth and pushing it out over the gills while closing the glottis. The muscle pattern of a hiccup is very similar. Under this hypothesis, the reflex survived because it does little harm. This is an idea, not an established fact.

History and culture

Charles Osborne of Iowa began to hiccup in 1922 and did not stop until 1990, a run of 68 years². At first he hiccuped about 40 times a minute². Later this slowed to about 20². He held down a job, married twice, and had eight children².

Dozens of folk cures exist: holding your breath, drinking from the far side of a glass, a spoon of sugar, a sudden fright. None has strong evidence. Most of them do change breathing and pressure in the chest, which may reset the reflex¹.