A hiccup involves the diaphragm, the sheet of muscles in the chest that controls breathing and separates the chest from the abdomen, and the vocal cords in the voice box.
When a sudden involuntary contraction of the diaphragm is accompanied by a quick closure of the vocal cords, the “hiccup” sound occurs.
The phrenic nerves, which run from neck to chest, normally coordinate the smooth contraction of the two leaves of the diaphragm, and hiccups may result from any irritation, mild or severe, anywhere along the path of a phrenic nerve.
The cause is usually not dangerous or even obvious.
They are common after eating a big meal or drinking a lot of alcohol.
In some rare cases, the cause may be a condition that severely irritates the diaphragm or its nerves.
These conditions include inflammation of the chest lining (pleurisy), pneumonia, some stomach and esophagus disorders, inflammation of the pancreas, alcoholism and hepatitis.
Attacks of hiccups are usually intermittent and brief and stop of their own accord.
In the rare cases where hiccuping is prolonged, drugs may be used, and very rarely, surgery to deaden nerves to paralyze half the diaphragm may be tried.
For garden-variety hiccups, this treatment often helps: gently massaging the back of the roof of the mouth with a cotton-tipped swab for a minute or so.